igc: Remove igc_*_mac_steering_filter() wrappers

With the previous two patches, igc_add_mac_steering_filter() and
igc_del_mac_steering_filter() became a pointless wrapper of
igc_add_mac_filter() and igc_del_mac_filter().

This patch removes these wrappers and update callers to call
igc_add_mac_filter() and igc_del_mac_filter() directly.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>