thermal: helpers: Introduce thermal_trip_is_bound_to_cdev()

Introduce a new helper function thermal_trip_is_bound_to_cdev() for
checking whether or not a given trip point has been bound to a given
cooling device.

The primary user of it will be the Tegra thermal driver.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/13545762.uLZWGnKmhe@rjwysocki.net