Linux <4.8 compat: submit_bio() rw arg

When using the two argument version of submit_bio() in kernel's prior
to 4.8 the first argument should be specified.  It's used by block
dump to report the bio direction.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Finix Yan <yancw@info2soft.com>
Closes #13006

module/os/linux/zfs/vdev_disk.c

@@ -446,7 +446,7 @@ vdev_submit_bio_impl(struct bio *bio)
 #ifdef HAVE_1ARG_SUBMIT_BIO
 	(void) submit_bio(bio);
 #else
-	(void) submit_bio(0, bio);
+	(void) submit_bio(bio_data_dir(bio), bio);
 #endif
 }