Having the driver struct at the end of the file isn't only more usual, it
also allows to drop a few forward declarations which are just useless
repetition.

While at it also move the MODULE_... macros to the end of the file.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>