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/meesc.h b/include/configs/meesc.h
index e5bf5d0..d002b97 100644
--- a/include/configs/meesc.h
+++ b/include/configs/meesc.h
@@ -59,6 +59,7 @@
  */
 
 /* Console output */
+#define CONFIG_AT91_GPIO			1
 #define CONFIG_ATMEL_USART			1
 #undef CONFIG_USART0
 #undef CONFIG_USART1