Fix bugs of saveing enviroment arguments into flash chip with different capacity

Enviroment arguments are saved into last 4K section of flash chip in original code,
it need to define the NVRAM_OFFS to tell bios from where to save them. Now use a global
flag "nvram_offs" in start.S to mark the location, its location was decided by the
compiler, so we needn't care it any longer.

Notice, this code assume "_start" is 0x80010000 during compiling pmon.bin. Otherwise,
this code need to change according the value of _start in conf/ld.script.

Target: Bonito3a780e

Targets/Bonito3a780e/Bonito/start.S

@@ -3088,7 +3088,6 @@ cache_init_finish:
 	.rdata
 	.align 5
 	.global ddr3_reg_data
-
 #include "loongson3a_ddr3_param.S"
 
 	.global watchdog_enable
@@ -3099,3 +3098,11 @@ watchdog_enable:
 	WatchDog_Enable
 	jr		ra
 	.end watchdog_enable
+
+	.text
+	.global  nvram_offs
+	.align 12
+nvram_offs:
+	.dword 0x0
+	.align 12
+	.dword 0x0

Targets/Bonito3a780e/Bonito/tgt_machdep.c

@@ -60,6 +60,8 @@
 #define STDIN		((kbd_available|usb_kbd_available)?3:0)
 //include "sys/sys/filio.h"
 
+extern char * nvram_offs;
+
 void	tgt_putchar (int);
 int
 tgt_printf (const char *fmt, ...)
@@ -1942,6 +1944,8 @@ tgt_netreset()
 /*
  *  Read in environment from NV-ram and set.
  */
+
+
 void
 tgt_mapenv(int (*func) __P((char *, char *)))
 {
@@ -1950,6 +1954,7 @@ tgt_mapenv(int (*func) __P((char *, char *)))
 	char *nvram;
 	int i;
 
+
         /*
          *  Check integrity of the NVRAM env area. If not in order
          *  initialize it to empty.
@@ -1959,7 +1964,7 @@ tgt_mapenv(int (*func) __P((char *, char *)))
     nvram = (char *)(tgt_flashmap())->fl_map_base;
 	printf("nvram=%08x\n",(unsigned int)nvram);
 	if(fl_devident(nvram, NULL) == 0 ||
-           cksum(nvram + NVRAM_OFFS, NVRAM_SIZE, 0) != 0) {
+           cksum(nvram + ((unsigned long)(&nvram_offs)-0x80010000), NVRAM_SIZE, 0) != 0) {
 #else
     nvram = (char *)malloc(512);
 	nvram_get(nvram);
@@ -1969,7 +1974,7 @@ tgt_mapenv(int (*func) __P((char *, char *)))
                 nvram_invalid = 1;
         }
         else {
-				nvram += NVRAM_OFFS;
+				nvram += ((unsigned long)(&nvram_offs)-0x80010000);
                 ep = nvram+2;;
 
                 while(*ep != 0) {
@@ -2046,6 +2051,7 @@ tgt_unsetenv(char *name)
         char *nvramsecbuf;
 	int status;
 
+
         if(nvram_invalid) {
                 return(0);
         }
@@ -2055,14 +2061,14 @@ tgt_unsetenv(char *name)
         nvram = (char *)(tgt_flashmap())->fl_map_base;
 
 	/* Map. Deal with an entire sector even if we only use part of it */
-        nvram += NVRAM_OFFS & ~(NVRAM_SECSIZE - 1);
+        nvram += ((unsigned long)(&nvram_offs)-0x80010000) & ~(NVRAM_SECSIZE - 1);
 	nvramsecbuf = (char *)malloc(NVRAM_SECSIZE);
 	if(nvramsecbuf == 0) {
 		printf("Warning! Unable to malloc nvrambuffer!\n");
 		return(-1);
 	}
         memcpy(nvramsecbuf, nvram, NVRAM_SECSIZE);
-	nvrambuf = nvramsecbuf + (NVRAM_OFFS & (NVRAM_SECSIZE - 1));
+	nvrambuf = nvramsecbuf + (((unsigned long)(&nvram_offs)-0x80010000) & (NVRAM_SECSIZE - 1));
 #else
         nvramsecbuf = nvrambuf = nvram = (char *)malloc(512);
 	nvram_get(nvram);
@@ -2147,7 +2153,7 @@ tgt_setenv(char *name, char *value)
         nvram = (char *)(tgt_flashmap())->fl_map_base;
 
 	/* Deal with an entire sector even if we only use part of it */
-        nvram += NVRAM_OFFS & ~(NVRAM_SECSIZE - 1);
+        nvram += ((unsigned long)(&nvram_offs)-0x80010000) & ~(NVRAM_SECSIZE - 1);
 #endif
 
         /* If NVRAM is found to be uninitialized, reinit it. */
@@ -2160,7 +2166,7 @@ tgt_setenv(char *name, char *value)
 #ifdef NVRAM_IN_FLASH
 		memcpy(nvramsecbuf, nvram, NVRAM_SECSIZE);
 #endif
-		nvrambuf = nvramsecbuf + (NVRAM_OFFS & (NVRAM_SECSIZE - 1));
+		nvrambuf = nvramsecbuf + (((unsigned long)(&nvram_offs)-0x80010000) & (NVRAM_SECSIZE - 1));
                 memset(nvrambuf, -1, NVRAM_SIZE);
                 nvrambuf[2] = '\0';
                 nvrambuf[3] = '\0';
@@ -2198,7 +2204,7 @@ tgt_setenv(char *name, char *value)
 #else
         memcpy(nvramsecbuf, nvram, NVRAM_SECSIZE);
 #endif
-	nvrambuf = nvramsecbuf + (NVRAM_OFFS & (NVRAM_SECSIZE - 1));
+	nvrambuf = nvramsecbuf + (((unsigned long)(&nvram_offs)-0x80010000) & (NVRAM_SECSIZE - 1));
 	/* Etheraddr is special case to save space */
 	if (strcmp("ethaddr", name) == 0) {
 		char *s = value;