xilinx: common: Remove zynq_board_read_rom_ethaddr()

Removing the zynq_board_read_rom_ethaddr() function as
xlnx,eeprom is not used anymore. As all board dts to use
nvmem alias instead of xlnx,eeprom.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20221017094818.17996-1-venkatesh.abbarapu@amd.com


Signed-off-by: Michal Simek <michal.simek@amd.com>