intel_minnow_max: Implemented pin mapping.

Signed-off-by: Henry Bruce <henry.bruce@intel.com>
mraa.c: Added minnow-max initialization

Signed-off-by: Henry Bruce <henry.bruce@intel.com>
gpio.c: Added error logging in mraa_gpio_init()

Signed-off-by: Henry Bruce <henry.bruce@intel.com>
blink_onboard.c: Added Minnow Max support

Signed-off-by: Henry Bruce <henry.bruce@intel.com>