Update vbus_hw.h

Added define __VBUS_HW_H__

bsp/qemu-vexpress-gemini/drivers/vbus_hw.h

@@ -26,6 +26,9 @@
  * 2015-01-07     Grissiom     init commit
  */
 
+#ifndef __VBUS_HW_H__
+#define __VBUS_HW_H__
+
 #include <rtthread.h>
 #include <stddef.h>
 #include <gic.h>
@@ -52,3 +55,5 @@ rt_inline void rt_vbus_smp_mb(void)
 {
     asm volatile ("dsb" : : : "memory");
 }
+
+#endif /* __VBUS_HW_H__ */