igc: Use netdev log helpers in igc_base.c

This patch coverts one pr_debug() call to hw_dbg() in order to keep log
output aligned with the rest of the driver. hw_dbg() is actually a macro
defined in igc_hw.h that expands to netdev_dbg().

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>