drm/i915: Include the sink/source/supported rates in debug output

TODO: Is there an actually nice way to print an array of ints?

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Sonika Jindal <sonika.jindal@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>