drm/i915: replace intel_infoframe_freq with VIDEO_DIP_FREQ_VSYNC

Simplifies things because for all the infoframes we care about,
we always send them on each vblank. Also, this gets rid of one
of the hw specific functions mislabelled with the intel_ prefix -
hsw will completely change how this works!

Acked-by: Paulo Zanoni <przanoni@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>