drm/i915/icl: Enable Sampler DFR

Sampler Dynamic Frequency Rebalancing (DFR) aims to reduce Sampler
power by dynamically changing its clock frequency in low-throughput
conditions. This patches enables it by default on Gen11.

v2: Wrong operation to clear the bit (Praveen)
v3: Rebased on top of the WA refactoring
v4: Move to icl_init_clock_gating, since it's not a WA (Rodrigo)
v5: C, not lisp (Chris)

Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Praveen Paneri <praveen.paneri@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@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/1525814984-20039-3-git-send-email-oscar.mateo@intel.com