drm/i915/icl: Fix DC9 Suspend for ICL.

Add missing block that takes care of inline intel_suspend_complete
for DC9 on ICL.

Daniele noticed this was part of original patch but missed on
on merged commit ("drm/i915/icl: Enable DC9 as lowest possible
 state during screen-off").

Fixes: 3e68928b ("drm/i915/icl: Enable DC9 as lowest possible state during screen-off")
Cc: Imre Deak <imre.deak@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Animesh Manna <animesh.manna@intel.com>
Cc: James Ausmus <james.ausmus@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
[Rodrigo added a commit message while merging]
Link: https://patchwork.freedesktop.org/patch/msgid/20181031202726.4021-1-anusha.srivatsa@intel.com