drm/i915/mtl: Add initial gt workarounds

This patch introduces initial gt workarounds for the MTL platform.

v2: drop redundant/stale comments specifying wa platforms affected
(Lucas).
v3: drop additional redundant stale comments (MattR)

Bspec: 66622

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230105234408.277750-1-matthew.s.atwood@intel.com