drm/i915/chv: Determine CHV slice/subslice/EU info

Total EU was already being detected on CHV, so we just add the
additional info parameters. The detection method is changed to
be more robust in the case of subslice fusing - we don't want
to trust the EU fuse bits corresponding to subslices which are
fused-off.

v2: Fixed subslice disable bitmasks and removed unnecessary ?
    operation (Ville)

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>