thermal: tsens: Check if TSENS device is enabled

TSENS (Temperature sensor) device is enabled before
the driver is probed and registers with the thermal sys.
Clients cannot read a valid temperature reading from the
TSENS device if it is not enabled or have the ability to
set temperature thresholds for notification. Therefore
check if the device is enabled as part of probe initialization.

Change-Id: I8e92b075b4b4b9fcf11481a0959a8e7c2e776dfc
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>