unix/unix_mphal: Adjust #if in mp_hal_stdin_rx_chr to improve format.

ports/unix/unix_mphal.c

@@ -147,7 +147,6 @@ static int call_dupterm_read(size_t idx) {
 #endif
 
 int mp_hal_stdin_rx_chr(void) {
-    unsigned char c;
 #if MICROPY_PY_OS_DUPTERM
     // TODO only support dupterm one slot at the moment
     if (MP_STATE_VM(dupterm_objs[0]) != MP_OBJ_NULL) {
@@ -162,10 +161,12 @@ int mp_hal_stdin_rx_chr(void) {
             c = '\r';
         }
         return c;
-    } else {
+    }
 main_term:;
 #endif
+
     MP_THREAD_GIL_EXIT();
+    unsigned char c;
     int ret = read(0, &c, 1);
     MP_THREAD_GIL_ENTER();
     if (ret == 0) {
@@ -174,9 +175,6 @@ int mp_hal_stdin_rx_chr(void) {
         c = '\r';
     }
     return c;
-#if MICROPY_PY_OS_DUPTERM
-    }
-#endif
 }
 
 void mp_hal_stdout_tx_strn(const char *str, size_t len) {