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/drivers/gpio/Makefile b/drivers/gpio/Makefile
index acba56c..d966082 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -25,6 +25,7 @@
 
 LIB 	:= $(obj)libgpio.a
 
+COBJS-$(CONFIG_AT91_GPIO)	+= at91_gpio.o
 COBJS-$(CONFIG_KIRKWOOD_GPIO)	+= kw_gpio.o
 COBJS-$(CONFIG_MX31_GPIO)	+= mx31_gpio.o
 COBJS-$(CONFIG_PCA953X)		+= pca953x.o