devicetree: Add vendor prefix for Nexbox

Nexbox is an IPTV set-top-box distributor, mainly with Amlogic SoCs:
        https://www.inexbox.comSigned-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -186,6 +186,7 @@ neonode		Neonode Inc.
 netgear	NETGEAR
 netlogic	Broadcom Corporation (formerly NetLogic Microsystems)
 netxeon		Shenzhen Netxeon Technology CO., LTD
+nexbox	Nexbox
 newhaven	Newhaven Display International
 nintendo	Nintendo
 nokia	Nokia