dt-bindings: nvmem: Add syscon to Vybrid OCOTP driver

Add syscon compatibility with Vybrid OCOTP driver binding. This is
required to access the UID.

Fixes: 62306994 ("nvmem: Add DT binding documentation for Vybrid OCOTP driver")
Signed-off-by: Chris Healy <cphealy@gmail.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>