igc: Use netdev log helpers in igc_ethtool.c

igc: Use netdev log helpers in igc_ethtool.c

In igc_ethtool.c we print log messages using dev_* helpers, generating
inconsistent output with the rest of the driver. Since this is a network
device driver, we should preferably use netdev_* helpers because they
append the interface name to the message, helping making sense the of
the logs.

This patch converts all dev_* calls to netdev_*.

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>