btrfs: remove pointless inode lookup when processing extrefs during log replay

At unlink_extrefs_not_in_log() we do an inode lookup of the directory but
we already have the directory inode accessible as a function argument, so
the lookup is redudant. Remove it and use the directory inode passed in as
an argument.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>