configs: add DM_SPI config option

This patch adds CONFIG_DM_SPI for all m68k boards using
the cf_spi.c driver (DSPI module).

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Angelo Dureghello <angelo@sysam.it>
diff --git a/configs/M54418TWR_nand_mii_defconfig b/configs/M54418TWR_nand_mii_defconfig
index c53c9d4..1c2d337 100644
--- a/configs/M54418TWR_nand_mii_defconfig
+++ b/configs/M54418TWR_nand_mii_defconfig
@@ -24,4 +24,5 @@
 CONFIG_SPI_FLASH_ATMEL=y
 CONFIG_MII=y
 CONFIG_SPI=y
+CONFIG_DM_SPI=y
 CONFIG_CF_SPI=y