imx7: Add include guards for include/asm/arch-mx7/sys_proto.h file

Signed-off-by: Lukasz Majewski <lukma@denx.de>

arch/arm/include/asm/arch-mx7/sys_proto.h

@@ -3,8 +3,12 @@
  *
  * SPDX-License-Identifier:	GPL-2.0+
  */
+#ifndef __SYS_PROTO_IMX7_
+#define __SYS_PROTO_IMX7_
 
 #include <asm/mach-imx/sys_proto.h>
 
 void set_wdog_reset(struct wdog_regs *wdog);
 enum boot_device get_boot_device(void);
+
+#endif /* __SYS_PROTO_IMX7_ */