igc: Remove obsolete circuit breaker registers

Part of circuit breaker registers is obsolete
and not applicable for i225 device.
This patch comes to clean up these registers.

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>