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/configs/stout_defconfig b/configs/stout_defconfig
index 69a914b..29d6420 100644
--- a/configs/stout_defconfig
+++ b/configs/stout_defconfig
@@ -66,7 +66,7 @@
 CONFIG_SYS_I2C_RCAR_IIC=y
 CONFIG_DM_MMC=y
 CONFIG_RENESAS_SDHI=y
-CONFIG_MTD=y
+CONFIG_DM_MTD=y
 CONFIG_MTD_DEVICE=y
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_SPANSION=y