igc: Use hardware routine for PHY reset

Summary:
The previously used software reset routine wasn't sufficient
to reset the PHY if the bootloader hadn't left the device in
an initialized state. This was seen with the onboard igc port
on an 11th-gen Intel NUC.

The software reset isn't used in the Linux driver so all related
code has been removed.

Tested on: Netgate 6100 onboard ports, a discrete PCIe I225-LM card,
and an 11th-gen Intel NUC.

Approved by: re (gjb)
Reported by: woodsb02
Tested by: woodsb02 (NUC)
Sponsored by: Rubicon Communications, LLC ("Netgate")

(cherry picked from commit 561cd74b1704ab76a3286733fb43da53b6892ea4)
(cherry picked from commit 267a39780ea8c89b7a89ca9e91dcfff02c69656f)