media: drop CONFIG_MEDIA_CONTROLLER_REQUEST_API

This config option was added during the development of the Request API
to make it easy to disable it.

The Request API is now stable so it is time to drop this option altogether.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>