configs: stm32f746-disco: Enable CONFIG_BLK

CONFIG_BLK config flag becomes mandatory, enable it.
Signed-off-by: NPatrice Chotard <patrice.chotard@st.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>

configs/stm32f746-disco_defconfig

@@ -40,7 +40,6 @@ CONFIG_CMD_FS_GENERIC=y
 CONFIG_OF_CONTROL=y
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_NETCONSOLE=y
-# CONFIG_BLK is not set
 CONFIG_DM_MMC=y
 # CONFIG_SPL_DM_MMC is not set
 CONFIG_ARM_PL180_MMCI=y