btrfs: remove pointless out labels from uuid-tree.c

btrfs: remove pointless out labels from uuid-tree.c

Some functions (btrfs_uuid_iter_rem() and btrfs_check_uuid_tree_entry())
have an 'out' label that does nothing but return, making it pointless.
Simplify this by removing the label and returning instead of gotos plus
setting the 'ret' variable.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>