ixgbe: Add ixgbe_x540 multiple header inclusion protection

Required to adopt x540 specific functions by E610 device.

Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Bharath R <bharath.r@intel.com>
Signed-off-by: Piotr Kwapulinski <piotr.kwapulinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: pkwapuli

drivers/net/ethernet/intel/ixgbe/ixgbe_x540.h

@@ -1,5 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-/* Copyright(c) 1999 - 2018 Intel Corporation. */
+/* Copyright(c) 1999 - 2024 Intel Corporation. */
+
+#ifndef _IXGBE_X540_H_
+#define _IXGBE_X540_H_
 
 #include "ixgbe_type.h"
 
@@ -17,3 +20,5 @@ int ixgbe_acquire_swfw_sync_X540(struct ixgbe_hw *hw, u32 mask);
 void ixgbe_release_swfw_sync_X540(struct ixgbe_hw *hw, u32 mask);
 void ixgbe_init_swfw_sync_X540(struct ixgbe_hw *hw);
 int ixgbe_init_eeprom_params_X540(struct ixgbe_hw *hw);
+
+#endif /* _IXGBE_X540_H_ */