media: platform/*/Kconfig: make manufacturer menus more uniform

Do some adjustments at the per-vendor Kconfig, adding a comment at
the beginning in order to identify the manufacturer, and adjust
a few entries to make them look more uniform.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com> # For sunxi
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

media: platform: Create vendor/{Makefile,Kconfig} files

Instead of placing multiple per-vendor entries at the
platform/{Makefile,Kconfig}, create them at the per-vendor
directories.

Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>