media: em28xx: Add support for Empia em2828X bridge

media: em28xx: Add support for Empia em2828X bridge

The empia em2828X usb bridge contains previous functionality,
but also contains an embedded video decoder. The implemented
capabilities include composite and s-video inputs, as well as
analog TV. Analog TV is expected in CVBS format, it must be
demodulated already.

Media controller decoder entity is included so pipeline
verification passes and graph is properly constructed.

Analog TV bits based off cx231xx driver.

Signed-off-by: Bradford Love <brad@nextdimension.cc>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
[hverkuil: fix a few minor checkpatch issues]