drm/i915/hdmi: Fix reg values for g4x_hdmi_connected

Paulo pointed out that gen4 re-used the SDVO registers for HDMI (the
separate HDMI registers where introduced with the first PCH) and so
g4x_hdmi_connected() never selected the right bit and always returned
disconnected.

Regression in

commit 8ec22b21
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri May 11 18:01:34 2012 +0100

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

Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>