drm/i915/hdmi: Query the live connector status bit for G4x

Similar to g4x_dp_detect() we should probe the PORT_HOTPLUG_STATUS as to
whether the connector is active prior to attempting to retrieve the EDID.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>