video: imxfb: Use module_platform_driver()

We have no reason to call fb_get_options() when registering module,
so move this call in the probe() and convert the driver to use
module_platform_driver() macro.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>