mtd: ensure MTD is compiled when there is a SPI NOR flash using MTD

MTD must be enabled when there is a SPI NOR flash using the
SPI_FLASH_MTD config entry.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
diff --git a/configs/da850evm_nand_defconfig b/configs/da850evm_nand_defconfig
index f929104..0e5c22b 100644
--- a/configs/da850evm_nand_defconfig
+++ b/configs/da850evm_nand_defconfig
@@ -54,6 +54,7 @@
 CONFIG_DA8XX_GPIO=y
 CONFIG_DM_I2C=y
 CONFIG_DM_MMC=y
+CONFIG_MTD=y
 CONFIG_DM_MTD=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_SYS_NAND_USE_FLASH_BBT=y