drm/i915: Add Wa_1407352427:icl,ehl

drm/i915: Add Wa_1407352427:icl,ehl

The workaround database now indicates we need to disable psdunit clock
gating as well.

v3:
 - Rebase on top of other workarounds that have landed.
 - Restrict cc:stable tag to 5.2+ since that's when ICL was first
   officially supported.

Bspec: 32354
Bspec: 33450
Bspec: 33451
Suggested-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: stable@vger.kernel.org # v5.2+
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191231190713.1549533-1-matthew.d.roper@intel.com