block: rename bio bi_rw to bi_opf

Since commit 63a4cc24867d, bio->bi_rw contains flags in the lower
portion and the op code in the higher portions. This means that
old code that relies on manually setting bi_rw is most likely
going to be broken. Instead of letting that brokeness linger,
rename the member, to force old and out-of-tree code to break
at compile time instead of at runtime.

No intended functional changes in this commit.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 46168ef..21dc00e 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1043,8 +1043,8 @@
 	unsigned long flags;
 	const int op = bio_op(bio);
 	const int rw = bio_data_dir(bio);
-	const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
-	const unsigned long do_flush_fua = (bio->bi_rw &
+	const unsigned long do_sync = (bio->bi_opf & REQ_SYNC);
+	const unsigned long do_flush_fua = (bio->bi_opf &
 						(REQ_PREFLUSH | REQ_FUA));
 	struct md_rdev *blocked_rdev;
 	struct blk_plug_cb *cb;
@@ -2318,7 +2318,7 @@
 		raid_end_bio_io(r1_bio);
 	} else {
 		const unsigned long do_sync
-			= r1_bio->master_bio->bi_rw & REQ_SYNC;
+			= r1_bio->master_bio->bi_opf & REQ_SYNC;
 		if (bio) {
 			r1_bio->bios[r1_bio->read_disk] =
 				mddev->ro ? IO_BLOCKED : NULL;