thermal/of: Fix reference leak in thermal_of_cm_lookup()

thermal/of: Fix reference leak in thermal_of_cm_lookup()

In thermal_of_cm_lookup(), tr_np is obtained via of_parse_phandle(), but
never released.

Use the __free(device_node) cleanup attribute to automatically release
the node and fix the leak.

Fixes: 423de5b5bc5b ("thermal/of: Fix cdev lookup in thermal_of_should_bind()")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
[ rjw: Changelog edits ]
Link: https://patch.msgid.link/20260124-thermal_of-v1-1-54d3416948cf@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>