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/ls1021aqds_nand_defconfig b/configs/ls1021aqds_nand_defconfig
index 48a1551..d6ae7ca 100644
--- a/configs/ls1021aqds_nand_defconfig
+++ b/configs/ls1021aqds_nand_defconfig
@@ -58,6 +58,7 @@
 CONFIG_SYS_FSL_DDR3=y
 CONFIG_DM_MMC=y
 CONFIG_FSL_ESDHC=y
+CONFIG_MTD=y
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_FLASH_CFI_DRIVER=y
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y