drm/i915: Make vlv/chv watermark debug print less cryptic

The magic numbers 0,1,2 aren't all that interesting for users perhaps.
Since we know what these watermark levels mean for VLV/CHV let's print
their names.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-6-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -1218,7 +1218,7 @@ static bool vlv_raw_plane_wm_compute(struct intel_crtc_state *crtc_state,
 
 out:
 	if (dirty)
-		DRM_DEBUG_KMS("%s wms: [0]=%d,[1]=%d,[2]=%d\n",
+		DRM_DEBUG_KMS("%s watermarks: PM2=%d, PM5=%d, DDR DVFS=%d\n",
 			      plane->base.name,
 			      crtc_state->wm.vlv.raw[VLV_WM_LEVEL_PM2].plane[plane_id],
 			      crtc_state->wm.vlv.raw[VLV_WM_LEVEL_PM5].plane[plane_id],