drm/i915/icl: WaCL2SFHalfMaxAlloc

This workarounds an issue with insufficient storage for the
CL2 and SF units.

v2: Renamed to Wa_1405766107
v3: Wrapped the commit message
v4: Rebased on top of the WA refactoring
v5: Added References (Mika)
v6:
  - Rebased
  - s/MACALLOC/MAXALLOC (Mika)
  - C, not lisp (Chris)

References: HSDES#1405766107
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/1525814984-20039-8-git-send-email-oscar.mateo@intel.com