ARM: socfpga: vining_fpga: Extract eth1 MAC from EEPROM

The EEPROM contains eth1 MAC address as well, use it.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Silvio Fricke <silvio.fricke@softing.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>