drm/i915/chv: Add CHV HW status to SSEU status

Collect the currently enabled counts of slice, subslice, and
execution units using the power gate control ack message
registers specific to Cherryview.

Slice/subslice/EU info and hardware status can now be
determined for CHV, so allow the debugfs SSEU status dump
to proceed for CHV devices.

Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>