thermal/debugfs: Move some statements from under thermal_dbg->lock

The tz_dbg local variable assignments in thermal_debug_tz_trip_up(),
thermal_debug_tz_trip_down(), and thermal_debug_update_trip_stats()
need not be carried out under thermal_dbg->lock, so move them from
under that lock (to avoid possible future confusion).

While at it, reorder local variable definitions in
thermal_debug_tz_trip_up() for more clarity.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>