btrfs: backref, constify some arguments

This constifies a few buffers used in the backref code.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Jeff Mahoney 2017-06-28 21:56:55 -06:00 • committed by David Sterba
commit 73980becae