drm/i915: Fix maxfifo watermark calc on vlv cursor planes

A typo resulted in the watermarks for cursor planes not being calculated
correctly.  Fixed the typo.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NThomas Daniel <thomas.daniel@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -1135,7 +1135,7 @@ static void vlv_compute_wm(struct intel_crtc *crtc)
 		case DRM_PLANE_TYPE_CURSOR:
 			for (level = 0; level < wm_state->num_levels; level++)
 				wm_state->sr[level].cursor =
-					wm_state->sr[level].cursor;
+					wm_state->wm[level].cursor;
 			break;
 		case DRM_PLANE_TYPE_PRIMARY:
 			for (level = 0; level < wm_state->num_levels; level++)