thermal: core: Drop thermal_zone_device_is_enabled()

thermal: core: Drop thermal_zone_device_is_enabled()

There are only two callers of thermal_zone_device_is_enabled()
and one of them call is under the zone lock and the other one uses
lockdep_assert_held() on that lock.  Thus the lockdep_assert_held()
in thermal_zone_device_is_enabled() is redundant and it could be
dropped, but then the function would merely become a wrapper around
a simple tz->mode check that is more convenient to do directly.

Accordingly, drop thermal_zone_device_is_enabled() altogether and update
its callers to check tz->mode directly as appropriate.

While at it, combine the tz->mode and tz->suspended checks in
__thermal_zone_device_update() because they are of a similar category
and if any of them evaluates to "true", the outcome is the same.

No intentinal functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/9353673.CDJkKcVGEf@rjwysocki.net