drm/i915/icl: Wa_1406838659

Disable CGPSF unit clock gating to prevent an issue.

v2: Rebased on top of the WA refactoring
v3: Added References (Mika)
v4:
  - Rebased
  - C, not lisp (Chris)
  - Remove unintentional whitespaces (Mika)
  - Fixed in C0 (Mika)

References: HSDES#1406838659
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/1525814984-20039-13-git-send-email-oscar.mateo@intel.com