dt-bindings: vendor-prefixes: Add Topwise

Topwise Communication Co,. Ltd. is a company based in Shenzhen. They
manufacture all kind of products but seem to be focusing on POS nowadays.

Signed-off-by: Pascal Roeleven <dev@pascalroeleven.nl>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Rob Herring <robh@kernel.org>