OMAP4 Thermal Framework: Add support for 12-bit GPADC on TWL6032

Changing the the algorithm for temperature calculation using a NTC termistor.
Now the temperature is selected from the table depending on the voltage,
and not from the ADC code. In this implementation, the dependence on the ADC resolution is lost.

Change-Id: I83d7b45d1b0c3b4a60089e3502aaeb91640a4ffd
Signed-off-by: Oleksandr_Tyshchenko <oleksandr.tyshchenko@ti.com>