drm/i915/xehpsdv: Add compute DSS type

Starting in XeHP, the concept of slice has been removed in favor of
DSS (Dual-Subslice) masks for various workload types. These workloads have
been divided into those enabled for geometry and those enabled for compute.

i915 currently maintains a single set of S/SS/EU masks for the device.
The goal of this patch set is to minimize the amount of impact to prior
generations while still giving the user maximum flexibility.

v2:
 - Generalize a comment about uapi access to geometry/compute masks; the
   proposed uapi has changed since the comment was first written, and
   will show up in a future series once the userspace code is published.
   (Lucas)

v3:
 - Eliminate unnecessary has_compute_dss flag.  (Lucas)
 - Drop unwanted comment change in uapi header.  (Lucas)

Bspec: 33117, 33118, 20376
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Steve Hampson <steven.t.hampson@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210806172901.1049133-1-matthew.d.roper@intel.com