msm-core: Update temp threshold only if sensor is disabled

The sensor structure used by the msm-core driver is continuously acted on
by the thermal driver. Changing the threshold temperatues without disabling
them could cause incorrect setting of the temperature at the thermal
sensor. To ensure thermal framework sees the changes, disable the sensor
before enabling the sensor with the updated values.

Change-Id: Ida8d3f511e5d600e87810c7a64de1a136f97aca9
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>