Just pass the intel_crtc around instead of dev_priv+pipe.

Also make intel_wait_for_pipe_off() static since it's only used in
intel_display.c.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Thomas Richter <richter@rus.uni-stuttgart.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>