net: Update hardware MAC address if it changes in env

When the ethaddr changes in the env, the hardware should also be updated
so that MAC filtering will work properly without resetting U-Boot.

Also remove the manual calls to set the hwaddr that was included in a
few drivers as a result of the framework not doing it.

Reported-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>