UBI: Set ubi_dev.type back to DEV_TYPE_NONE upon failing initialization

With this patch we set the type back to NONE upon failing UBI partition
initialization. Otherwise further calls to the UBI subsystem would try
to really access the non-existing UBI partition.

Thanks to Michael Lawnick for pointing this out.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/common/cmd_ubi.c b/common/cmd_ubi.c
index fd33a67..4c35892 100644
--- a/common/cmd_ubi.c
+++ b/common/cmd_ubi.c
@@ -508,6 +508,7 @@
 		err = ubi_dev_scan(ubi_dev.mtd_info, ubi_dev.part_name);
 		if (err) {
 			printf("UBI init error %d\n", err);
+			ubi_dev.type = DEV_TYPE_NONE;
 			return err;
 		}