thermal/core: Allocate the thermal class dynamically

thermal/core: Allocate the thermal class dynamically

Use class_create() instead of a statically allocated struct class.

This allows the thermal class to be managed through a dynamically
allocated class object and avoids keeping a static class instance
around.

Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
[ rjw: Added __ro_after_init to thermal_class ]
[ rjw: Used temporary local var to store class_create() return value ]
Link: https://patch.msgid.link/20260508180511.1306659-4-daniel.lezcano@oss.qualcomm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>