media: platform: omap3isp: move config to its own file

In order to better organize the platform/Kconfig, place
omap3isp-specific config stuff on a separate Kconfig file.

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