media: platform: rename omap/ to ti/omap/

As the end goal is to have platform drivers split by vendor,
rename omap/ to ti/omap/.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>