usb: pd: Add captive Type C cable type

The USB Power Delivery Specification R3.0 adds a captive cable type
to the "USB Type-C plug to USB Type-C/Captive" field (Bits 19-18,
Passive/Active Cable VDO, Table 6-38 & 6-39).

Add the corresponding definition to the Cable VDO header. Also add a
helper macro to get the Type C cable connector type, when provided
the cable VDO.

Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Benson Leung <bleung@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20201116201150.2919178-2-pmalani@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>