arm: zynq: Enable BLK when needed

There is no reason to enable BLK by default for all boards which is just
increasing memory footprint for memory contrained boards like cse.
zc770s are also saving some space.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zc770_xm011_defconfig b/configs/zynq_zc770_xm011_defconfig
index 2f1205a..e350ae0 100644
--- a/configs/zynq_zc770_xm011_defconfig
+++ b/configs/zynq_zc770_xm011_defconfig
@@ -28,6 +28,7 @@
 # CONFIG_CMD_NFS is not set
 CONFIG_CMD_CACHE=y
 CONFIG_SPL_DM_SEQ_ALIAS=y
+CONFIG_BLK=y
 CONFIG_FPGA_XILINX=y
 # CONFIG_MMC is not set
 CONFIG_NAND=y