net: eth-uclass: Write MAC address to hardware after probe

In order for the device to use the proper MAC address, which can have
been configured in the environment prior to the device being registered,
ensure that the MAC address is written after the device has been probed.
For devices that are registered before the network stack is initialized,
this is already done during eth_initialize(). If the Ethernet device is
on a bus that is not initialized on early boot, such as PCI, the device
is not available at the time eth_initialize() is called, so we need the
MAC address programming to also happen after probe.

Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>