btrfs: pass walk_control structure to add_inode_ref() and helpers

Instead of passing the transaction, subvolume root and log tree as
arguments to add_inode_ref() and its helpers (__add_inode_ref(),
unlink_refs_not_in_log(), unlink_extrefs_not_in_log() and
unlink_old_inode_refs()), pass the walk_control structure as we can
access all of those from the structure. This reduces the number of
arguments passed and it's going to be needed by an incoming change
that improves error reporting for log replay.

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