drm/i915/hdmi: Cache EDID for a detection cycle

drm/i915/hdmi: Cache EDID for a detection cycle

As we may query the edid multiple times following a detect, record the
EDID found during output discovery and reuse it. This is a separate
issue from caching the output EDID across detection cycles.

v2: Also hookup the force() callback for audio detection when the user
forces the connection status.
v3: Ville spots a typo, s/==/!=/

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>