drm/i915: SDVO hotplug have different interrupt status bits for i915/i965/g4x

drm/i915: SDVO hotplug have different interrupt status bits for i915/i965/g4x

commit 084b612ecf8e59973576b2f644e6949609c79375 upstream.

Note that gen3 is the only platform where we've got the bit
definitions right, hence the workaround of disabling sdvo hotplug
support on i945g/gm is not due to misdiagnosis of broken hotplug irq
handling ...

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: add some blurb about sdvo hotplug fail on i945g/gm I've
wondered about while reviewing.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2:
 - Adjust context
 - Handle all three cases in i915_driver_irq_postinstall() as there
   are not separate functions for gen3 and gen4+
 - Carry on using IS_SDVOB() in intel_sdvo_init()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>