thermal: core: Send trip crossing notifications at init time if needed

If a trip point is already exceeded by the zone temperature at the
initialization time, no trip crossing notification is send regarding
this even though mitigation should be started then.

Address this by rearranging the code in handle_thermal_trip() to
send a trip crossing notification for trip points already exceeded
by the zone temperature initially which also allows to reduce its
size by using the observation that the initialization and regular
trip crossing on the way up become the same case then.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>