UBIFS: Add ubifsumount command to unmount an active volume

This new ubifsumount command allows the user to unmount a previously
mounted UBIFS volume.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 39e3efe..63b2164 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -824,7 +824,7 @@
  * through mounting (error path cleanup function). So it has to make sure the
  * resource was actually allocated before freeing it.
  */
-static void ubifs_umount(struct ubifs_info *c)
+void ubifs_umount(struct ubifs_info *c)
 {
 	dbg_gen("un-mounting UBI device %d, volume %d", c->vi.ubi_num,
 		c->vi.vol_id);