drm/edid: Move dvi_dual/max_tmds_clock to drm_display_info

We have the drm_display_info for storing information about the sink, so
let's move dvi_dual and max_tmds_clock in there.

v2: Deal with superfluous code shuffling
    Document dvi_dual and max_tmds_clock too

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com> (v1)
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1475070703-6435-5-git-send-email-ville.syrjala@linux.intel.com