igc: Fix the typo in igc_base.h header definition

Add the underline for the _IGC_BASE_H_.
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>

drivers/net/ethernet/intel/igc/igc_base.h

 /* SPDX-License-Identifier: GPL-2.0 */
 /* Copyright (c)  2018 Intel Corporation */
 
-#ifndef _IGC_BASE_H
-#define _IGC_BASE_H
+#ifndef _IGC_BASE_H_
+#define _IGC_BASE_H_
 
 /* forward declaration */
 void igc_rx_fifo_flush_base(struct igc_hw *hw);