btrfs: fix bitmap leak when loading free space cache on duplicate entry

[ Upstream commit 320d8dc612660da84c3b70a28658bb38069e5a9a ]

If we failed to link a free space entry because there's already a
conflicting entry for the same offset, we free the free space entry but
we don't free the associated bitmap that we had just allocated before.
Fix that by freeing the bitmap before freeing the entry.

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>