drm/i915/dg2: Add support for DC5 state

With the latest DMC in place, enabling DC5 on DG2.

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220728183641.55692-1-anusha.srivatsa@intel.com

drivers/gpu/drm/i915/display/intel_display_power.c

@@ -908,7 +908,7 @@ static u32 get_allowed_dc_mask(const struct drm_i915_private *dev_priv,
 		return 0;
 
 	if (IS_DG2(dev_priv))
-		max_dc = 0;
+		max_dc = 1;
 	else if (IS_DG1(dev_priv))
 		max_dc = 3;
 	else if (DISPLAY_VER(dev_priv) >= 12)