btrfs: remove use btrfs_remove_free_space_cache instead of variant

We are calling __btrfs_remove_free_space_cache everywhere to cleanup the
block group free space, however we can just use
btrfs_remove_free_space_cache and pass in the block group in all of
these places.  Then we can remove __btrfs_remove_free_space_cache and
rename __btrfs_remove_free_space_cache_locked to
__btrfs_remove_free_space_cache.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>