devicetree: bindings: Add vendor prefix for Shenzhen Xunlong Software

Shenzhen Xunlong Software CO.,Limited is a SBC vendor, which produces
the "Orange Pi" series of SBCs.

Add a vendor prefix for it. This prefix is already used in many
Allwinner H3 boards.
Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -329,6 +329,7 @@ x-powers	X-Powers
 xes	Extreme Engineering Solutions (X-ES)
 xillybus	Xillybus Ltd.
 xlnx	Xilinx
+xunlong	Shenzhen Xunlong Software CO.,Limited
 zarlink	Zarlink Semiconductor
 zii	Zodiac Inflight Innovations
 zte	ZTE Corp.