drm/i915: Update kerneldoc for intel_wm_need_update()

drivers/gpu/drm/i915/intel_display.c:10708: warning: Function parameter or member 'cur' not described in 'intel_wm_need_update'
drivers/gpu/drm/i915/intel_display.c:10708: warning: Function parameter or member 'new' not described in 'intel_wm_need_update'
drivers/gpu/drm/i915/intel_display.c:10708: warning: Excess function parameter 'plane' description in 'intel_wm_need_update'
drivers/gpu/drm/i915/intel_display.c:10708: warning: Excess function parameter 'state' description in 'intel_wm_need_update'

References: cd1d3ee9 ("drm/i915: Use intel_ types more consistently for watermark code (v2)")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181231143505.2523-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_display.c

@@ -10673,8 +10673,8 @@ static void intel_crtc_destroy(struct drm_crtc *crtc)
 
 /**
  * intel_wm_need_update - Check whether watermarks need updating
- * @plane: drm plane
- * @state: new plane state
+ * @cur: current plane state
+ * @new: new plane state
  *
  * Check current plane state versus the new one to determine whether
  * watermarks need to be recalculated.