drm/i915: PCH_ prefix for transcoder timings

drm/i915: PCH_ prefix for transcoder timings

While at it, also extract a common helper to copy the timings from the
cpu transcoder to the pch transcoder. That way it's really explicit
how the lpt transcoder is hardcoded.

v2:
- Re-align #defines properly (Paulo).
- Use cpu_transcoder when copying pipe timings (Paulo).
- s/intel_pch_transcoder_enable/intel_pch_transcoder_set_timings/
  since we already have a pch transcoder enable function, and this is
  clearer, too.
- Fixup 80 char line overflow in intel_display.c. I've opted to ignore
  this in i915_reg.h and i915_ums.c since meh.

Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>