ARM: mvebu: define CONFIG_BLK for db-88f6820-amc

db-88f6820-amc uses CONFIG_DM_USB and CONFIG_USB_STORAGE already so
define CONFIG_BLK to prepare it for full conversion to DM.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/configs/db-88f6820-amc_defconfig b/configs/db-88f6820-amc_defconfig
index dd58198..9068a58 100644
--- a/configs/db-88f6820-amc_defconfig
+++ b/configs/db-88f6820-amc_defconfig
@@ -43,6 +43,9 @@
 CONFIG_DEFAULT_DEVICE_TREE="armada-385-amc"
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_SPL_OF_TRANSLATE=y
+CONFIG_BLK=y
+# CONFIG_SPL_BLK is not set
+# CONFIG_BLOCK_CACHE is not set
 CONFIG_DM_I2C=y
 CONFIG_SYS_I2C_MVTWSI=y
 # CONFIG_MMC is not set