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/ls1021aiot_qspi_defconfig b/configs/ls1021aiot_qspi_defconfig
index 8420876..d5e3f4e 100644
--- a/configs/ls1021aiot_qspi_defconfig
+++ b/configs/ls1021aiot_qspi_defconfig
@@ -24,6 +24,7 @@
 CONFIG_FSL_CAAM=y
 CONFIG_DM_MMC=y
 CONFIG_FSL_ESDHC=y
+CONFIG_MTD=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_ATMEL=y
 CONFIG_SPI_FLASH_STMICRO=y