bio: first step in sanitizing the bio->bi_rw flag testing

Get rid of any functions that test for these bits and make callers
use bio_rw_flagged() directly. Then it is at least directly apparent
what variable and flag they check.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 7140909..89e7681 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -90,7 +90,7 @@
 
 	if (uptodate)
 		multipath_end_bh_io(mp_bh, 0);
-	else if (!bio_rw_ahead(bio)) {
+	else if (!bio_rw_flagged(bio, BIO_RW_AHEAD)) {
 		/*
 		 * oops, IO error:
 		 */
@@ -144,7 +144,7 @@
 	const int rw = bio_data_dir(bio);
 	int cpu;
 
-	if (unlikely(bio_barrier(bio))) {
+	if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER))) {
 		bio_endio(bio, -EOPNOTSUPP);
 		return 0;
 	}