Gen12 has dual-subslices (DSS), which compared to gen11 subslices have
some duplicated resources/paths. Although DSS behave similarly to 2
subslices, instead of splitting this and presenting userspace with bits
not directly representative of hardware resources, present userspace
with a subslice_mask made up of DSS bits instead.

v2: GEM_BUG_ON on mask size (Lionel)

Bspec: 29547
Bspec: 12247
Cc: Kelvin Gardiner <kelvin.gardiner@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
CC: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com> #v1
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: NJames Ausmus <james.ausmus@intel.com>
Signed-off-by: NOscar Mateo <oscar.mateo@intel.com>
Signed-off-by: NSudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: NStuart Summers <stuart.summers@intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: NLucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190913075137.18476-2-chris@chris-wilson.co.ukSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>