media: dt: bindings: tegra-vde: Document new optional Memory Client reset property

Recently binding of the Memory Controller has been extended, exposing
the Memory Client reset controls and hence it is now a reset controller.
Tegra video-decoder device is among the Memory Controller reset users,
document the new optional VDE HW reset property.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>