drm/i915/dmc: Load DMC on DG2

Add Support for DC states on Dg2.

v2: Add dc9 as the max supported DC states and disable DC5.
v3: set max_dc to 0. (Imre)

Cc: Imre Deak <imre.deak@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com&gt;(v1)>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220504202213.740200-2-anusha.srivatsa@intel.com