mtd: Use MTD_BLOCK_MAJOR instead of the magic number

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
diff --git a/drivers/mtd/mtdblock_ro.c b/drivers/mtd/mtdblock_ro.c
index 92759a9..70d27b4 100644
--- a/drivers/mtd/mtdblock_ro.c
+++ b/drivers/mtd/mtdblock_ro.c
@@ -70,7 +70,7 @@
 
 static struct mtd_blktrans_ops mtdblock_tr = {
 	.name		= "mtdblock",
-	.major		= 31,
+	.major		= MTD_BLOCK_MAJOR,
 	.part_bits	= 0,
 	.blksize 	= 512,
 	.readsect	= mtdblock_readsect,