arm64: versal: Move common board dtb search

Move the exisiting function of getting board dtb from versal to a common
Xilinx folder.

Signed-off-by: Ibai Erkiaga <ibai.erkiaga-elorza@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/versal/Makefile b/board/xilinx/versal/Makefile
index 2b81276..e9307d7 100644
--- a/board/xilinx/versal/Makefile
+++ b/board/xilinx/versal/Makefile
@@ -5,3 +5,4 @@
 #
 
 obj-y	:= board.o
+obj-y	+= ../common/board.o