ARM: at91: declare header name

Add the header and define the macro to prevent multiple inclusion
like the others headers.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/mach-at91/pm.h

+/*
+ * AT91 Power Management
+ *
+ * Copyright (C) 2005 David Brownell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+#ifndef __ARCH_ARM_MACH_AT91_PM
+#define __ARCH_ARM_MACH_AT91_PM
+
 #ifdef CONFIG_ARCH_AT91RM9200
 #include <mach/at91rm9200_mc.h>
 
@@ -95,3 +108,5 @@ static inline u32 sdram_selfrefresh_enable(void)
 	cpu_do_idle()
 
 #endif
+
+#endif