thermal: core: Pass trip descriptor to thermal_trip_crossed()

In preparation for subsequent changes, modify thermal_trip_crossed()
to take a trip descriptor pointer instead of a pointer to struct
thermal_trip and propagate this change to thermal_zone_trip_down().

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/10547668.nUPlyArG6x@rjwysocki.net