e1000e: convert to real ndo_set_rx_mode

Commit afc4b13d (net: remove use of ndo_set_multicast_list in
drivers) changed e1000e to use the ndo_set_rx_mode entry point,
but didn't implement the unicast address programming
functionality. Implement it to achieve the ability to add unicast
addresses.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>