arm: zynq: Add identification string to Xilinx boards

It is good to see this string to make sure that u-boot which runs on the
board is the same which should run there.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zc770_xm012_defconfig b/configs/zynq_zc770_xm012_defconfig
index a8338f5..3893780 100644
--- a/configs/zynq_zc770_xm012_defconfig
+++ b/configs/zynq_zc770_xm012_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_ZYNQ=y
 CONFIG_SYS_TEXT_BASE=0x4000000
+CONFIG_IDENT_STRING=" Xilinx Zynq ZC770 XM012"
 CONFIG_SPL_STACK_R_ADDR=0x200000
 # CONFIG_SPL_FAT_SUPPORT is not set
 CONFIG_DEFAULT_DEVICE_TREE="zynq-zc770-xm012"