can: gs_usb: document GS_CAN_FEATURE_GET_STATE

Document the new feature ("GS_CAN_FEATURE_GET_STATE") that indicates
that the state of the CAN controller can be queried with the new
GS_USB_BREQ_GET_STATE control message.
Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Link: https://lore.kernel.org/all/20221019221016.1659260-7-mkl@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/gs_usb.c

@@ -66,6 +66,7 @@ enum gs_usb_breq {
 	GS_USB_BREQ_BT_CONST_EXT,
 	GS_USB_BREQ_SET_TERMINATION,
 	GS_USB_BREQ_GET_TERMINATION,
+	GS_USB_BREQ_GET_STATE,
 };
 
 enum gs_can_mode {
@@ -135,6 +136,7 @@ struct gs_device_config {
 /* GS_CAN_FEATURE_BT_CONST_EXT BIT(10) */
 /* GS_CAN_FEATURE_TERMINATION BIT(11) */
 #define GS_CAN_MODE_BERR_REPORTING BIT(12)
+/* GS_CAN_FEATURE_GET_STATE BIT(13) */
 
 struct gs_device_mode {
 	__le32 mode;
@@ -176,7 +178,8 @@ struct gs_device_termination_state {
 #define GS_CAN_FEATURE_BT_CONST_EXT BIT(10)
 #define GS_CAN_FEATURE_TERMINATION BIT(11)
 #define GS_CAN_FEATURE_BERR_REPORTING BIT(12)
-#define GS_CAN_FEATURE_MASK GENMASK(12, 0)
+#define GS_CAN_FEATURE_GET_STATE BIT(13)
+#define GS_CAN_FEATURE_MASK GENMASK(13, 0)
 
 /* internal quirks - keep in GS_CAN_FEATURE space for now */