btrfs: reduce parameters of btrfs_pin_extent_for_log_replay

Both callers of btrfs_pin_extent_for_log_replay expand the parameters to
extent buffer members. We can simply pass the extent buffer instead.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>