btrfs: rename io_failure_record::bio_flags to compress_type

The bio_flags is now used to store unchanged compress type, so unify
that.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>