mmap: added mmap io to gpio

* added function to gpio to use mmap
* changed board definition format around mmap io (fast-gpio)
* Intel Galileo Rev D updated to follow changed definitions

* Example performing mmap io to pin 2 added.

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>

include/maa_internal.h

@@ -62,3 +62,10 @@ maa_spi_bus_t* maa_setup_spi(int bus);
  * @return the pwm pin_info_t of that IO pin
  */
 maa_pin_t* maa_setup_pwm(int pin);
+
+/** Setup gpio mux to go straight to SoC, galileo.
+ *
+ * @param pin physical pin to use
+ * @return maa_mmap_pin_t
+ */
+maa_mmap_pin_t* maa_setup_mmap_gpio(int pin);