USB Storage, add meaningful return value

This patch changes the "usb storage" command to return success if it
finds a USB storage device, otherwise it returns error.

Signed-off-by: Markus Klotzbuecher <mk@denx.de>
diff --git a/common/usb_storage.c b/common/usb_storage.c
index 443d785..81d2f92 100644
--- a/common/usb_storage.c
+++ b/common/usb_storage.c
@@ -188,17 +188,20 @@
  * show info on storage devices; 'usb start/init' must be invoked earlier
  * as we only retrieve structures populated during devices initialization
  */
-void usb_stor_info(void)
+int usb_stor_info(void)
 {
 	int i;
 
-	if (usb_max_devs > 0)
+	if (usb_max_devs > 0) {
 		for (i = 0; i < usb_max_devs; i++) {
 			printf ("  Device %d: ", i);
 			dev_print(&usb_dev_desc[i]);
+			return 0;
 		}
-	else
+	} else {
 		printf("No storage devices, perhaps not 'usb start'ed..?\n");
+		return 1;
+	}
 }
 
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