dt-bindings: connector: Add SVDM VDO properties

Add bindings of VDO properties of USB PD SVDM so that they can be
used in device tree.

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Kyle Tso <kyletso@google.com>
Link: https://lore.kernel.org/r/20210205033415.3320439-7-kyletso@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>