Optional, selects the exact phy address that should be connected
and function fecmxc_initialize will try to initialize it.
+CONFIG_FEC_FIXED_SPEED
+ Optional, selects a fixed speed on the MAC interface without asking some
+ phy. This is usefull if there is a direct MAC <-> MAC connection, for
+ example if the CPU is connected directly via the RGMII interface to a
+ ethernet-switch.
Reading the ethaddr from the SoC eFuses:
if CONFIG_FEC_MXC is defined and the U-Boot environment does not contain the