MIPS: bootm.c: add support for 'prep' and 'go' subcommands

The bootm command supports subcommands since long time
however those subcommands are not yet usable on MIPS.

The patch is based on the ARM implementation, and it adds
support for the 'prep' and 'go' subcommands only.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>

arch/mips/lib/bootm.c

@@ -104,8 +104,19 @@ static void boot_jump_linux(bootm_headers_t *images)
 int do_bootm_linux(int flag, int argc, char * const argv[],
 			bootm_headers_t *images)
 {
-	if ((flag != 0) && (flag != BOOTM_STATE_OS_GO))
-		return 1;
+	/* No need for those on MIPS */
+	if (flag & BOOTM_STATE_OS_BD_T || flag & BOOTM_STATE_OS_CMDLINE)
+		return -1;
+
+	if (flag & BOOTM_STATE_OS_PREP) {
+		boot_prep_linux(images);
+		return 0;
+	}
+
+	if (flag & BOOTM_STATE_OS_GO) {
+		boot_jump_linux(images);
+		return 0;
+	}
 
 	boot_prep_linux(images);
 	boot_jump_linux(images);