drm/i915/icl: WaGAPZPriorityScheme

The default GAPZ arbitrer priority value at power-on has been found
to be incorrect.

v2: Now renamed to Wa_1405543622
v3: Rebased on top of the WA refactoring
v4: Added HSDES reference number (Mika)
v5:
  - Rebased
  - C, not lisp (Chris)

References: HSDES#1405543622
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1525814984-20039-4-git-send-email-oscar.mateo@intel.com