arm: zynq: Enable DM_GPIO when needed

There are two reasons for doing this change.
There is still !DM driver for xilinx soft gpio IP and especially it is
saving some space for memory constrained boards like cse (almost ~400B).

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zc770_xm013_defconfig b/configs/zynq_zc770_xm013_defconfig
index 08f8ade..e9c86cb 100644
--- a/configs/zynq_zc770_xm013_defconfig
+++ b/configs/zynq_zc770_xm013_defconfig
@@ -31,6 +31,7 @@
 CONFIG_SPL_DM_SEQ_ALIAS=y
 CONFIG_BLK=y
 CONFIG_FPGA_XILINX=y
+CONFIG_DM_GPIO=y
 # CONFIG_MMC is not set
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_BAR=y