drm/tve200: Add new driver for TVE200

drm/tve200: Add new driver for TVE200

This adds a new DRM driver for the Faraday Technology TVE200
block. This "TV Encoder" encodes a ITU-T BT.656 stream and can
be found in the StorLink SL3516 (later Cortina Systems CS3516)
as well as the Grain Media GM8180.

I do not have definitive word from anyone at Faraday that this
IP block is theirs, but it bears the hallmark of their 3-digit
version code (200) and is used in two SoCs from completely
different companies. (Grain Media was fully owned by Faraday
until it was transferred to NovoTek this january, and
Faraday did lots of work on the StorLink SoCs.)

The D-Link DIR-685 uses this in connection with the Ilitek
ILI9322 panel driver that supports BT.656 input, while the
GM8180 apparently has been used with the Cirrus Logic CS4954
digital video encoder. The oldest user seems to be
something called Techwall 2835.

This driver is heavily inspired by Eric Anholt's PL111
driver and therefore I have mentioned all the ancestor authors
in the header file.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20170820100557.24991-2-linus.walleij@linaro.org