drm/i915: Stop using encoder->type in intel_ddi_enable_transcoder_func()

intel_ddi_enable_transcoder_func() already has the crtc state so we can
use that instead of the untrustworthy encoder->type.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019133721.11794-5-ville.syrjala@linux.intel.com


Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>