drm/doc: Fix missing kerneldoc for drm_dp_helper.c

Never added when the DP validation code was added.
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1468612088-9721-5-git-send-email-daniel.vetter@ffwll.ch

include/drm/drm_dp_helper.h

@@ -747,7 +747,14 @@ struct drm_dp_aux {
 	struct mutex hw_mutex;
 	ssize_t (*transfer)(struct drm_dp_aux *aux,
 			    struct drm_dp_aux_msg *msg);
-	unsigned i2c_nack_count, i2c_defer_count;
+	/**
+	 * @i2c_nack_count: Counts I2C NACKs, used for DP validation.
+	 */
+	unsigned i2c_nack_count;
+	/**
+	 * @i2c_defer_count: Counts I2C DEFERs, used for DP validation.
+	 */
+	unsigned i2c_defer_count;
 };
 
 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,