thermal: core: Represent suspend-related thermal zone flags as bits

thermal: core: Represent suspend-related thermal zone flags as bits

Instead of using two separate fields in struct thermal_zone_device for
representing flags related to thermal zone suspend, represent them
explicitly as bits in one u8 "state" field.

Subsequently, that field will be used for addressing race conditions
related to thermal zone initialization and exit.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/7733910.EvYhyI6sBW@rjwysocki.net
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>