drm: Describe dp_rev for drm_dp_set_phy_test_pattern

drivers/gpu/drm/drm_dp_helper.c:1598: warning: Function parameter or member 'dp_rev' not described in 'drm_dp_set_phy_test_pattern'
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200516212330.13633-3-chris@chris-wilson.co.uk

drivers/gpu/drm/drm_dp_helper.c

@@ -1588,6 +1588,7 @@ EXPORT_SYMBOL(drm_dp_get_phy_test_pattern);
  * drm_dp_set_phy_test_pattern() - set the pattern to the sink.
  * @aux: DisplayPort AUX channel
  * @data: DP phy compliance test parameters.
+ * @dp_rev: DP revision to use for compliance testing
  *
  * Returns 0 on success or a negative error code on failure.
  */