drm/dp: Add DP_DPCD_QUIRK_NO_SINK_COUNT

drm/dp: Add DP_DPCD_QUIRK_NO_SINK_COUNT

CH7511 eDP->LVDS bridge doesn't seem to set SINK_COUNT properly
causing i915 to detect it as disconnected. Add a quirk to ignore
SINK_COUNT on these devices.

Cc: David S. <david@majinbuu.com>
Cc: Peteris Rudzusiks <peteris.rudzusiks@gmail.com>
Tested-by: Peteris Rudzusiks <peteris.rudzusiks@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105406
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528140650.19230-1-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com> #irc