drm/i915: more virtual south bridge detection

commit 39bfcd5235e07e95ad3e70eab8e0b85db181de9e upstream.

Commit "30c964a6 drm/i915: Detect virtual south bridge" detects and
handles the southbridge emulated by vmware esx.  Add the ich9 south
bridge emulated by 'qemu -M q35'.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>