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/pico-imx7d_bl33_defconfig b/configs/pico-imx7d_bl33_defconfig
index 6633115..51d3514 100644
--- a/configs/pico-imx7d_bl33_defconfig
+++ b/configs/pico-imx7d_bl33_defconfig
@@ -48,6 +48,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_DM_MMC=y
 CONFIG_FSL_USDHC=y
+CONFIG_MTD=y
 CONFIG_PHYLIB=y
 CONFIG_MII=y
 CONFIG_PINCTRL=y