mtd: rename CONFIG_MTD_DEVICE -> CONFIG_MTD

Like in Linux, just use CONFIG_MTD to compile the MTD stack.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
diff --git a/configs/rock_defconfig b/configs/rock_defconfig
index 3ce9aa1..0858a1f 100644
--- a/configs/rock_defconfig
+++ b/configs/rock_defconfig
@@ -42,6 +42,7 @@
 CONFIG_LED=y
 CONFIG_MMC_DW=y
 CONFIG_MMC_DW_ROCKCHIP=y
+CONFIG_MTD=y
 CONFIG_SF_DEFAULT_SPEED=20000000
 CONFIG_PINCTRL=y
 CONFIG_DM_PMIC=y