configs: stm32f469-disco: Enable CONFIG_BLK

CONFIG_BLK config flag becomes mandatory, enable it.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

configs/stm32f469-discovery_defconfig

@@ -26,7 +26,6 @@ CONFIG_CMD_FAT=y
 CONFIG_CMD_FS_GENERIC=y
 CONFIG_OF_CONTROL=y
 CONFIG_OF_EMBED=y
-# CONFIG_BLK is not set
 CONFIG_DM_MMC=y
 CONFIG_ARM_PL180_MMCI=y
 CONFIG_MTD_NOR_FLASH=y