ARM64: zynqmp: Add support for reading MAC from eeprom

Add support for on board eeprom with programmed MAC for using in u-boot
to have uniq address for every board.
Most of the time uniq MAC address is on a label on the board.
If address is not programmed use these command to program it.

On zcu102:
ZynqMP> mm.b 0
00000000: 00 ? 00
00000001: a0 ? 0a
00000002: 35 ? 35
00000003: 02 ? 02
00000004: 00 ? ef
00000005: 00 ? 67
00000006: 00 ? q
i2c dev 5
i2c write 0 54 20 6
i2c md 54 20

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