igc: Add support for PF

This patch adds the basic defines and structures needed by the PF for
operation. With this it is possible to bring up the interface,
but without being able to configure any of the filters on
the interface itself.
Add skeleton for a function pointers.

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>