ACPI: thermal: Move acpi_thermal_driver definition

Move the definition of the acpi_thermal_driver structure closer to the
initialization code that registes the driver, so some function forward
declarations can be dropped.

Also move the module information to the end of the file where it is
usually located.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>