drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get()

drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get()

intel_crtc->config->cpu_transcoder isn't yet filled out when
intel_crtc_mode_get() gets called during output probing, so we should
not use it there. Instead intel_crtc_mode_get() figures out the correct
transcoder on its own, and that's what we should use.

If the BIOS boots LVDS on pipe B, intel_crtc_mode_get() would actually
end up reading the timings from pipe A instead (since PIPE_A==0),
which clearly isn't what we want.

It looks to me like this may have been broken by
commit eccb140bca67 ("drm/i915: hw state readout&check support for cpu_transcoder")
as that one removed the early initialization of cpu_transcoder from
intel_crtc_init().

Cc: [email protected]
Cc: [email protected]
Cc: Rob Kramer <[email protected]>
Cc: Daniel Vetter <[email protected]>
Reported-by: Rob Kramer <[email protected]>
Fixes: eccb140bca67 ("drm/i915: hw state readout&check support for cpu_transcoder")
References: https://lists.freedesktop.org/archives/dri-devel/2016-April/104142.html
Signed-off-by: Ville Syrjälä <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit e30a154b5262b967b133b06ac40777e651045898)
Signed-off-by: Rodrigo Vivi <[email protected]>