arm: xilinx_versal_virt: Add a devicetree file

Add an empty file to prevent build errors when building with
CONFIG_OF_SEPARATE enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/xilinx_versal_virt_defconfig b/configs/xilinx_versal_virt_defconfig
index 1159862..f0ec263 100644
--- a/configs/xilinx_versal_virt_defconfig
+++ b/configs/xilinx_versal_virt_defconfig
@@ -7,6 +7,7 @@
 CONFIG_SYS_MEMTEST_START=0x00000000
 CONFIG_SYS_MEMTEST_END=0x00001000
 CONFIG_DM_GPIO=y
+CONFIG_DEFAULT_DEVICE_TREE="xilinx-versal-virt"
 CONFIG_CMD_FRU=y
 CONFIG_DEFINE_TCM_OCM_MMAP=y
 CONFIG_COUNTER_FREQUENCY=100000000