devicetree: add vendor prefix for Khadas

Khadas is a new sub-brand of "Shenzhen Wesion Technology Co., Ltd.".
They are developing Amlogic and Rockchip based "DIY boxes" (single board
computers): http://khadas.com/
They are best know for their latest product: the Khadas VIM (an Amlogic
GXL S905X based SBC).
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -160,6 +160,7 @@ jedec	JEDEC Solid State Technology Association
 karo	Ka-Ro electronics GmbH
 keithkoep	Keith & Koep GmbH
 keymile	Keymile GmbH
+khadas	Khadas
 kinetic Kinetic Technologies
 kosagi	Sutajio Ko-Usagi PTE Ltd.
 kyo	Kyocera Corporation