Make the gpio.h header self contained

There are several subsystems in the kernel that just include this file in
order to support gpio drivers, make this header include by itself the needed
headers to avoid errors at compilation

include/asm-arm/arch-davinci/gpio.h

@@ -13,6 +13,10 @@
 #ifndef	__DAVINCI_GPIO_H
 #define	__DAVINCI_GPIO_H
 
+#include <asm/io.h>
+#include "hardware.h"
+#include "io.h"
+
 /*
  * basic gpio routines
  *