autostart: unify duplicated logic into the bootm code

Rather than having a bunch of random commands handle autostart behavior,
unify the logic in a single place.  This also fixes building of these

different commands when bootm is disabled.

Acked-by: Matthew McClintock <msm@freescale.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index 1966da4..272d879 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -708,6 +708,21 @@
 	return 1;
 }
 
+int bootm_maybe_autostart(cmd_tbl_t *cmdtp, const char *cmd)
+{
+	const char *ep = getenv("autostart");
+
+	if (ep && !strcmp(ep, "yes")) {
+		char *local_args[2];
+		local_args[0] = (char *)cmd;
+		local_args[1] = NULL;
+		printf("Automatic boot of image at addr 0x%08lX ...\n", load_addr);
+		return do_bootm(cmdtp, 0, 1, local_args);
+	}
+
+	return 0;
+}
+
 /**
  * image_get_kernel - verify legacy format kernel image
  * @img_addr: in RAM address of the legacy format image to be verified