mtd: rename CONFIG_MTD -> CONFIG_DM_MTD

CONFIG_MTD must be reserved for the MTD core. Like any other
subsystem, prefix the symbol by DM when it comes to DM support.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
[trini: Add Kconfig files]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/mtd/mtd_uboot.c b/drivers/mtd/mtd_uboot.c
index 55742275..7c6c9ac 100644
--- a/drivers/mtd/mtd_uboot.c
+++ b/drivers/mtd/mtd_uboot.c
@@ -99,7 +99,7 @@
 	return -EINVAL;
 }
 
-#if IS_ENABLED(CONFIG_MTD)
+#if IS_ENABLED(CONFIG_DM_MTD)
 static void mtd_probe_uclass_mtd_devs(void)
 {
 	struct udevice *dev;