lm4f: Switch GPIOs to using AHB bus ***WARNING***

The AHB bus allows faster control of GPIO pins versus the older APB bus.
The GPIO ports A through H default on the APB bus. Change the GPIOx
defines in gpio.h to use the base address of the AHB bus.

There's another reason to use the AHB bus: ports K tand highercan only be
accessed via the AHB bus.

***WARNING***
To work, GPIO acces to the AHB bus must be explictly enabled via the
GPIOHBCTL register. Without any additional change, this patch will break
any code using the older APB bus. If the GPIOHBCTL is not properly
modified, any acces to the GPIO register will cause a hard fault.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

include/libopencm3/lm4f/gpio.h

@@ -43,14 +43,14 @@ LGPL License Terms @ref lgpl_license
 /* --- Convenience macros -------------------------------------------------- */
 
 /* GPIO port base addresses (for convenience) */
-#define GPIOA				GPIOA_APB_BASE
-#define GPIOB				GPIOB_APB_BASE
-#define GPIOC				GPIOC_APB_BASE
-#define GPIOD				GPIOD_APB_BASE
-#define GPIOE				GPIOE_APB_BASE
-#define GPIOF				GPIOF_APB_BASE
-#define GPIOG				GPIOG_APB_BASE
-#define GPIOH				GPIOH_APB_BASE
+#define GPIOA				GPIOA_BASE
+#define GPIOB				GPIOB_BASE
+#define GPIOC				GPIOC_BASE
+#define GPIOD				GPIOD_BASE
+#define GPIOE				GPIOE_BASE
+#define GPIOF				GPIOF_BASE
+#define GPIOG				GPIOG_BASE
+#define GPIOH				GPIOH_BASE
 
 /* GPIO number definitions (for convenience) */
 #define GPIO0				(1 << 0)