thermal: core: Fix disabled trip point check in handle_thermal_trip()

Commit bc840ea5 ("thermal: core: Do not handle trip points with
invalid temperature") added a check for invalid temperature to the
disabled trip point check in handle_thermal_trip(), but that check was
added at a point when the trip structure has not been initialized yet.

This may cause handle_thermal_trip() to skip a valid trip point in some
cases, so fix it by moving the check to a suitable place, after
__thermal_zone_get_trip() has been called to populate the trip
structure.

Fixes: bc840ea5

 ("thermal: core: Do not handle trip points with invalid temperature")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>