mtd: blkdevs: fix switch-bool compilation warning

With gcc 5.1 I get:
warning: switch condition has boolean value [-Wswitch-bool]
Signed-off-by: Tomer Barletz <barletz@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/mtd_blkdevs.c

@@ -97,14 +97,13 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr,
 	if (req->cmd_flags & REQ_DISCARD)
 		return tr->discard(dev, block, nsect);
 
-	switch(rq_data_dir(req)) {
-	case READ:
+	if (rq_data_dir(req) == READ) {
 		for (; nsect > 0; nsect--, block++, buf += tr->blksize)
 			if (tr->readsect(dev, block, buf))
 				return -EIO;
 		rq_flush_dcache_pages(req);
 		return 0;
-	case WRITE:
+	} else {
 		if (!tr->writesect)
 			return -EIO;
 
@@ -113,9 +112,6 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr,
 			if (tr->writesect(dev, block, buf))
 				return -EIO;
 		return 0;
-	default:
-		printk(KERN_NOTICE "Unknown request %u\n", rq_data_dir(req));
-		return -EIO;
 	}
 }