thermal: intel: int340x: Add locking to int340x_thermal_get_trip_type()

In order to prevent int340x_thermal_get_trip_type() from possibly
racing with int340x_thermal_read_trips() invoked by int3403_notify()
add locking to it in analogy with int340x_thermal_get_trip_temp().

Fixes: 6757a7ab

 ("thermal: intel: int340x: Protect trip temperature from concurrent updates")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>