Btrfs: fix search_ioctl key advance

key->type is u8, not u64.

fs/btrfs/ioctl.c: In function 'copy_to_sk':
fs/btrfs/ioctl.c:1024: warning: comparison is always true due to limited range of data type

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ioctl.c

@@ -1000,7 +1000,7 @@ static noinline int copy_to_sk(struct btrfs_root *root,
 advance_key:
 	if (key->offset < (u64)-1)
 		key->offset++;
-	else if (key->type < (u64)-1)
+	else if (key->type < (u8)-1)
 		key->type++;
 	else if (key->objectid < (u64)-1)
 		key->objectid++;