e1000e: Support RXFCS feature flag.

This enables enabling/disabling reception of the Ethernet
FCS.  This can be useful when sniffing packets.

For e1000e, enabling RXFCS can change the default
behaviour for how the NIC handles CRC.  Disabling RXFCS
will take the NIC back to defaults, which can be configured
as part of the module options.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>