add a new AT91 GPIO driver

* add a real AT91 GPIO driver instead of header inline code
* resolve the mixing of port and pins
* change board config files to use new driver
* add macros to gpio to realize backward compatibility

Signed-off-by: Jens Scharsig <js_at_ng@scharsoft.de>
diff --git a/include/configs/at91sam9261ek.h b/include/configs/at91sam9261ek.h
index 832b1cd..63b55d2 100644
--- a/include/configs/at91sam9261ek.h
+++ b/include/configs/at91sam9261ek.h
@@ -52,6 +52,7 @@
 /*
  * Hardware drivers
  */
+#define CONFIG_AT91_GPIO	1
 #define CONFIG_ATMEL_USART	1
 #undef CONFIG_USART0
 #undef CONFIG_USART1