media: cxusb: add analog mode support for Medion MD95700

This patch adds support for analog part of Medion 95700 in the cxusb
driver.

What works:
* Video capture at various sizes with sequential fields,
* Input switching (TV Tuner, Composite, S-Video),
* TV and radio tuning,
* Video standard switching and auto detection,
* Radio mode switching (stereo / mono),
* Unplugging while capturing,
* DVB / analog coexistence.

What does not work yet:
* Audio,
* VBI,
* Picture controls.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: remove left-over commented-out debug message]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>