thermal: msm8960_tsens: Read TSENS temperature

Add kernel API to read TSENS temperature for clients
in the kernel space. Currently the TSENS driver only
supports reading the TSENS temperature from the
thermal sys.

Split the TSENS initialization into two parts.
First is to perform the initial calibration that is
used to convert the raw ADC code to Degrees Celcius
and initialize the TSENS HW. Second is to register the
TSENS driver to the linux thermal framework and create
the temperature zones that will be accessed by the
Thermal daemon to set thresholds, read the temperature
and receive notifications.

Change-Id: Id2305a7aa755e1e9cfaecd8b5c1870ed05d9b5e9
Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>