Trip temperatures are read using ACPI methods and stored in the memory
during zone initializtion and when the firmware sends a notification for
change. This trip temperature is returned when the thermal core calls via
callback get_trip_temp().

But it is possible that while updating the memory copy of the trips when
the firmware sends a notification for change, thermal core is reading the
trip temperature via the callback get_trip_temp(). This may return invalid
trip temperature.

To address this add a mutex to protect the invalid temperature reads in
the callback get_trip_temp() and int340x_thermal_read_trips().

Fixes: 5fbf7f27 ("Thermal/int340x: Add common thermal zone handler")
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: 5.0+ <stable@vger.kernel.org> # 5.0+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>