btrfs: provide enumeration for __merge_refs mode argument

Replace hardcoded numeric values for __merge_refs 'mode' argument
with descriptive constants.

Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Reviewed-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Edmund Nadolski 2017-03-16 10:04:33 -06:00 • committed by David Sterba
commit f58d88b336