drm/i915/vlv: Workaround a punit issue in DDR data rate for 1333.

For DDR data rate reporting by Punit in PUNIT_GPU_FREQ_STS, the actual
data encoding is 00b=800, 01b=1066, 10b=1333, 11b=1333.

Some premium VLV sku will get the DDR_DATA_RATE set as 11.  As a result,
the turbo frequency reporting will be incorrect without this workaround.
Signed-off-by: Chon Ming Lee <chon.ming.lee@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -5322,12 +5322,7 @@ static void valleyview_init_clock_gating(struct drm_device *dev)
 		dev_priv->mem_freq = 1333;
 		break;
 	case 3:
-		/*
-		 * Probably a BIOS/Punit bug, or a new platform we don't
-		 * support yet.
-		 */
-		WARN(1, "invalid DDR freq detected, assuming 800MHz\n");
-		dev_priv->mem_freq = 800;
+		dev_priv->mem_freq = 1333;
 		break;
 	}
 	DRM_DEBUG_DRIVER("DDR speed: %d MHz", dev_priv->mem_freq);