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/Kconfig b/board/xilinx/Kconfig
index 37bec5f..4f29033 100644
--- a/board/xilinx/Kconfig
+++ b/board/xilinx/Kconfig
@@ -39,3 +39,10 @@
 	     before the build.
 
 endif
+
+config VERSAL_OF_BOARD_DTB_ADDR
+	hex
+	default 0x1000
+	depends on OF_BOARD
+	help
+	  Offset in the memory where the board configuration DTB is placed.