btrfs: rename btrfs_release_extent_buffer_page

The function used to release one page (and always the first one), but
not anymore since a50924e3a4d7fccb0ecfbd4 ("btrfs: drop constant param
from btrfs_release_extent_buffer_page").  Update the name and comment.

Signed-off-by: David Sterba <dsterba@suse.com>
1 file changed