igc: Remove unneeded code

Remove the 'igc_get_link_up_info_base method' from igc_base.c file.
Use the 'igc_get_speed_and_duplex_copper' method directly and reduce
the code redundancy.

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>