video: omap: convert drivers/video/omap/* to use module_platform_driver()

This patch converts the drivers in drivers/video/omap/* to use the
module_platform_driver() macro which makes the code smaller and a bit
simpler.

Cc: Jonathan McDowell <noodles@earth.li>
Cc: Cory Maccarrone <darkstar6262@gmail.com>
Cc: Laurent Gonzalez <palmte.linux@free.fr>
Cc: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>