[media] omap_vout: fix section mismatch

Fix the following warning by using platform_driver_probe() instead of
platform_driver_register():

WARNING: drivers/media/video/omap/omap-vout.o(.data+0x24): Section
mismatch in reference from the variable omap_vout_driver to the function
.init.text:omap_vout_probe()
The variable omap_vout_driver references
the function __init omap_vout_probe()

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Tested-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>