drm/i915/tgl: Tigerlake only has global MOCS registers

drm/i915/tgl: Tigerlake only has global MOCS registers

Until Icelake, each engine had its own set of 64 MOCS registers. In
order to simplify, Tigerlake moves to only 64 Global MOCS registers,
which are no longer part of the engine context. Since these registers
are now global, they also only need to be initialized once.

>From Gen12 onwards, MOCS must specify the target cache (3:2) and LRU
management (5:4) fields and cannot be programmed to 'use the value from
Private PAT', because these fields are no longer part of the PPAT. Also
cacheability control (1:0) field has changed, 00 no longer means 'use
controls from page table', but uncacheable (UC).

v2 (Lucas):
    - Move the changes to the fault registers to a separate commit - the
      old ones overlap with the range used by the new global MOCS
      (requested by Daniele)
v3 (Lucas):
    - Clarify comment about setting the unused entries to the same value
      of index 0, that is the invalid entry (requested by Daniele)
    - Move changes to DONE_REG and ERROR_GEN6 to a separate commit
      (requested by Daniele)

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Tomasz Lis <tomasz.lis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190730180407.5993-5-lucas.demarchi@intel.com