ARM: at91: generic.h: Add include safe guards

The generic.h header file doesn't have any safe guards against multiple
inclusion. It only worked so far because all the symbols defined in it were
extern, but this is a rather fragile assumption.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/mach-at91/generic.h b/arch/arm/mach-at91/generic.h
index f42b049..31cba6d 100644
--- a/arch/arm/mach-at91/generic.h
+++ b/arch/arm/mach-at91/generic.h
@@ -8,6 +8,9 @@
  * published by the Free Software Foundation.
  */
 
+#ifndef _AT91_GENERIC_H
+#define _AT91_GENERIC_H
+
 #include <linux/clkdev.h>
 #include <linux/of.h>
 #include <linux/reboot.h>
@@ -84,3 +87,5 @@
 					  struct device_node *parent);
 
 extern u32 at91_get_extern_irq(void);
+
+#endif /* _AT91_GENERIC_H */