ixgbe: Remove driver config for KX4 PHY

The KX4 PHY is configured by the NVM.  Currently, the driver is overwriting
the config; remove the code associated with KX4 configuration.

Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>