igc: Fix NFC rule overwrite cases

When the 'loc' argument is passed in ethtool, the input rule overwrites
any rule present in that location. In this situation we must disable the
old rule otherwise it is left enabled in hardware. This patch fixes
the issue by always calling igc_disable_nfc_rule() when deleting the
old rule, no matter the value of 'input' argument.

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>