thermal: tsens: Update TSENS property for reading efuse data

TSENS (temperature sensor) controller provides capability
to program the gain and offset for individual sensors so that
the controller reports the temperature. The efuse information
for gain and offset can be read during boot and programmed
at boot initialization and the application TSENS driver
does not need to support reading from the efuse region.
Update the property for reading the tsens efuse as optional
for such cases.

Change-Id: Icd637fcd264565b06bcb90f8e6f7b26c8d112f24
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>