fp5280g2: Setting the mac address on first boot.

Tested: Built a fp5280g2 image and manually clear the `ethaddr` env in
u-boot, and verify the mac address is synced to u-boot.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I96c1422721efa55a3ee72504a021a0381fce695c
2 files changed