medfield: Add Thermal Driver

This is the basic thermal sensor driver for Intel MID platform using the
Medfield chipset. It plugs in via the thermal drivers and provides sensor
readings for the device sensors.

Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>