xilinx: Move zynq_board_read_rom_ethaddr to shared location

Zynq and ZynqMP are sharing similar code and there is no reason to do
code duplication. Move zynq_board_read_rom_ethaddr() to common file for
easier conversion to DM.
Use ZynqMP version that's why also add CONFIG_ZYNQ_EEPROM_BUS to Syzygy
which is only one Zynq board which is using this feature.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynqmp/Makefile b/board/xilinx/zynqmp/Makefile
index 960b81f..80f8ca7 100644
--- a/board/xilinx/zynqmp/Makefile
+++ b/board/xilinx/zynqmp/Makefile
@@ -4,6 +4,7 @@
 # Michal Simek <michal.simek@xilinx.com>
 
 obj-y	:= zynqmp.o
+obj-y	+= ../common/board.o
 
 ifneq ($(CONFIG_XILINX_PS_INIT_FILE),"")
 PS_INIT_FILE := $(shell cd $(srctree); readlink -f $(CONFIG_XILINX_PS_INIT_FILE))