media: platform: sun8i-di: move config to its own file

In order to better organize the platform/Kconfig, place
sun8i-di-specific config stuff on a separate Kconfig file.

Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>