drm/rect: update kerneldoc for drm_rect_clip_scaled()

This was forgotten in f96bdf56 ("drm/rect: Handle rounding errors
in drm_rect_clip_scaled, v3.")

Spotted while reviewing patches from Ville touching this area.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Fixes: f96bdf56 ("drm/rect: Handle rounding errors in drm_rect_clip_scaled, v3.")
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191126145213.380079-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_rect.c

@@ -81,11 +81,13 @@ static u32 clip_scaled(int src, int dst, int *clip)
  * @clip: clip rectangle
  *
  * Clip rectangle @dst by rectangle @clip. Clip rectangle @src by the
- * same amounts multiplied by @hscale and @vscale.
+ * the corresponding amounts, retaining the vertical and horizontal scaling
+ * factors from @src to @dst.
  *
  * RETURNS:
+ *
  * %true if rectangle @dst is still visible after being clipped,
- * %false otherwise
+ * %false otherwise.
  */
 bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
 			  const struct drm_rect *clip)