dt-bindings: Add Kingnovel vendor prefix

Their domain name is spelled kingnoval, but textually Kingnovel.

Cc: ada@kingnoval.com
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>