thermal/core: Add dedicated release callback for thermal zones

thermal/core: Add dedicated release callback for thermal zones

The thermal class release callback currently handles thermal zone
cleanup by checking the device name prefix.

Move the thermal zone cleanup to a dedicated struct device release
callback.  This avoids relying on device names to select the release
path and keeps the thermal zone lifetime handling local to the thermal
zone object.

Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/20260508180511.1306659-3-daniel.lezcano@oss.qualcomm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>