usb: typec: tcpm: Fix up PR_SWAP when vsafe0v is signalled

During PR_SWAP, When TCPM is in PR_SWAP_SNK_SRC_SINK_OFF, vbus is
expected to reach VSAFE0V when source turns off vbus. Do not move
to SNK_UNATTACHED state when this happens.

Fixes: 28b43d3d ("usb: typec: tcpm: Introduce vsafe0v for vbus")
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://lore.kernel.org/r/20210517192112.40934-1-badhri@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpm.c

@@ -5155,6 +5155,9 @@ static void _tcpm_pd_vbus_vsafe0v(struct tcpm_port *port)
 				tcpm_set_state(port, SNK_UNATTACHED, 0);
 		}
 		break;
+	case PR_SWAP_SNK_SRC_SINK_OFF:
+		/* Do nothing, vsafe0v is expected during transition */
+		break;
 	default:
 		if (port->pwr_role == TYPEC_SINK && port->auto_vbus_discharge_enabled)
 			tcpm_set_state(port, SNK_UNATTACHED, 0);