mtd: ensure MTD is compiled when CMD_MTDPARTS is selected

MTD support must be enabled when using mtdparts. Indeed, functions
like get_mtd_info(), get_mtd_device() and put_mtd_device() are in
drivers/mtd/mtd_uboot.c and are built only with CONFIG_MTD.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
diff --git a/configs/lion-rk3368_defconfig b/configs/lion-rk3368_defconfig
index aacac7e..218646a 100644
--- a/configs/lion-rk3368_defconfig
+++ b/configs/lion-rk3368_defconfig
@@ -64,6 +64,7 @@
 CONFIG_ROCKCHIP_GPIO=y
 CONFIG_MMC_DW=y
 CONFIG_MMC_DW_ROCKCHIP=y
+CONFIG_MTD=y
 CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_PHY_MICREL=y