Now that we ask to adjust the crtc timings for stereo modes, the correct
pipe_src_w and pipe_src_h can be found in crtc_vdisplay and crtc_hdisplay.

v2: Add comment about why pipe_src_w/h need to be set afert
    set_crtcinfo() (Daniel Vetter)
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>