media: TDA1997x: replace video detection routine

media: TDA1997x: replace video detection routine

The TDA1997x (HDMI receiver) driver currently uses a specific video
format detection scheme. The frame (or field in interlaced mode), line
and HSync pulse durations are compared to those of known, standard video
modes. If a match is found, the mode is assumed to be detected,
otherwise -ERANGE is returned (then possibly ignored). This means that:
- another mode with similar timings will be detected incorrectly
  (e.g. 2x faster clock and lines twice as long)
- non-standard modes will not work.

This patch replaces this scheme with a direct read of geometry
registers. This way all modes recognized by the chip are supported.

In interlaced modes, the code assumes the V sync signal has the same
duration for both fields. While this may be not necessarily true,
I can't see any way to get the "other" V sync width. This is most
probably harmless.

All tests have been performed on Gateworks' Ventana GW54xx board, with
a TDA19971 chip.

Signed-off-by: Krzysztof Hałasa <khalasa@piap.pl>
Tested-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>