Documentation: devicetree: add vendor prefix for Pine64

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Chen-Yu Tsai <wens@csie.org>
[Maxime: Change title prefix to match the usual style]
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -208,6 +208,7 @@ parade	Parade Technologies Inc.
 pericom	Pericom Technology Inc.
 phytec	PHYTEC Messtechnik GmbH
 picochip	Picochip Ltd
+pine64	Pine64
 pixcir  PIXCIR MICROELECTRONICS Co., Ltd
 plathome	Plat'Home Co., Ltd.
 plda	PLDA