drm/i915: convert PIPE_MSA_MISC to transcoder

Same as the other registers. This one also appeared on Haswell for the
first time, so that's why we are renaming it.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>