aio: added configuration within platform data.

* Allows for different bit shifting for each platform.
* New functions added for obtaining this information
* mraa_adc_raw_bits
* mraa_adc_supported_bits

* Update board information to include this. AIO module changed to allow
* use of the new board data

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

src/intel_galileo_rev_g.c

@@ -39,6 +39,8 @@ mraa_intel_galileo_gen2()
     b->phy_pin_count = 20;
     b->gpio_count = 14;
     b->aio_count = 6;
+    b->adc_raw = 12;
+    b->adc_supported = 10;
 
     b->pins = (mraa_pininfo_t*) malloc(sizeof(mraa_pininfo_t)*MRAA_INTEL_GALILEO_GEN_2_PINCOUNT);