drm/bridge: Add timing support to dumb VGA DAC

This extends the dumb VGA DAC bridge to handle the THS8134A
and THS8134B VGA DACs in addition to those already handled.

We assign the proper timing data to the pointer inside the
bridge struct so display controllers that need to align their
timings to the bridge can pick it up and work from there.

Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180112074854.9560-3-linus.walleij@linaro.org