Enable IDE DMA support for ls3b780e and ls3bserver board

Original code miss IDE DMA suport in configure file, now add and
enable the option.The bug as "http://www.loongson.org/dev/bugzilla
/show_bug.cgi?id=409" described won't appear any more. It pass test
on both ls3b780e and ls3bserver board.

Target:Bonito3b780e,Bonito3bserver

Targets/Bonito3b780e/conf/Bonito.3b780e

@@ -195,6 +195,7 @@ select      mod_usb_kbd
 
 
 #### IDE controllers
+option                 IDE_DMA
 pciide* 	at pci ? dev ? function ? flags 0x0000
 
 #### IDE hard drives

Targets/Bonito3bserver/conf/Bonito.3bserver

@@ -198,6 +198,7 @@ select      mod_usb_kbd
 
 
 #### IDE controllers
+option                 IDE_DMA
 pciide* 	at pci ? dev ? function ? flags 0x0000
 
 #### IDE hard drives