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_xm010_defconfig b/configs/zynq_zc770_xm010_defconfig
index f38ce4f..8fa6671 100644
--- a/configs/zynq_zc770_xm010_defconfig
+++ b/configs/zynq_zc770_xm010_defconfig
@@ -38,6 +38,7 @@
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_SPL_DM_SEQ_ALIAS=y
 CONFIG_FPGA_XILINX=y
+CONFIG_DM_GPIO=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_ZYNQ=y
 CONFIG_SPI_FLASH=y