meta-ampere: mtmitchell: set BMC MAC address from FRU

Update the MAC address via BMC FRU data, the MAC address is based on
"Board extra information 1". BMC FRU device is detected based on i2c bus
index and address.

Tested:
1. Clear environment and then reboot BMC.
2. Wait for BMC to boot complete, check for eth0 to have MAC Address the
same value defined in FRU at Board Extra.

Signed-off-by: Thang Tran <thuutran@amperecomputing.com>
Change-Id: I5d644109143e4d600b92e23e3f1627986e827768