drm/i915: Forcing a modeset when resetting HDMI link

With fastboot enabled in gen9+ it broke the HDMI reset as just
setting mode_changed to true causes a fastset and here we want a full
modeset that will disable and then enable the encoder of this HDMI
link actually, so setting connectors_changed instead that will cause
modeset as desired.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190302003349.19189-3-jose.souza@intel.com