Now that we track the cpu transcoder we need accurately in the pipe
config we can finally fix up the transcoder check. With the current
code eDP on port D will be broken since we'd errornously cut the
power.

For reference see

commit 2124b72e
Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
Date:   Fri Mar 22 14:07:23 2013 -0300

    drm/i915: don't disable the power well yet

v2:
- Kill the now outdated comment (Paulo)
- Add the missing crtc->base.enabled check and consolidate it (Paulo)
- Smash all checks together, looks neater that way.

v3: Kill the unused encoder variable.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>