drm/i915/icl: Wa_1406680159

Disable GWL clock gating to prevent an issue that might
cause hangs.

v2: Rebased on top of the WA refactoring
v3: Wa_2201832410 officially merged with Wa_1406680159
v4: Added References (Mika)
v5:
  - Rebased
  - C, not lisp (Chris)
  - Add reference where WA is better explained (Rodrigo)
  - Add reference to WA that got merged with this

References: HSDES#1406681710
References: HSDES#1406680159
References: HSDES#2201832410
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1525814984-20039-11-git-send-email-oscar.mateo@intel.com