arm64: Add Xilinx ZynqMP support

Add basic Xilinx ZynqMP arm64 support.
Serial and SD is supported.
It supports emulation platfrom ep108 and QEMU.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xilinx_zynqmp_defconfig b/configs/xilinx_zynqmp_defconfig
new file mode 100644
index 0000000..8b6aa70
--- /dev/null
+++ b/configs/xilinx_zynqmp_defconfig
@@ -0,0 +1,14 @@
+CONFIG_ARM=y
+CONFIG_TARGET_XILINX_ZYNQMP=y
+CONFIG_CMD_BDI=y
+CONFIG_CMD_BOOTD=y
+CONFIG_CMD_RUN=y
+CONFIG_CMD_IMI=y
+CONFIG_CMD_SAVEENV=y
+CONFIG_CMD_FLASH=y
+CONFIG_CMD_ECHO=y
+CONFIG_CMD_SOURCE=y
+CONFIG_CMD_TIME=y
+CONFIG_CMD_MISC=y
+CONFIG_CMD_TIMER=y
+CONFIG_DEFAULT_DEVICE_TREE="zynqmp"