thermal/drivers/rcar_gen3_thermal: Fix device initialization

The thermal zone is registered before the device is register and the
thermal coefficients are calculated, providing a window for very
incorrect readings.

The reason why the zone was register before the device was fully
initialized was that the presence of the set_trips() callback is used to
determine if the driver supports interrupt or not, as it is not defined
if the device is incapable of interrupts.

Fix this by using the operations structure in the private data instead
of the zone to determine if interrupts are available or not, and
initialize the device before registering the zone.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20230208190333.3159879-4-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>