drm/i915: explicitly cast pipe -> cpu_transcoder
drm/i915: explicitly cast pipe -> cpu_transcoder

This makes sparse happy and also makes it a bit more obvious where we
pull off this trick - after all we're only allowed to do it eithe as a
default or on platforms where there is no disdinction between the pipe
and the cpu transcoder.

Reviewed-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs