dt-bindings: Add vendor prefix for Adafruit

This adds a device tree vendor prefix for Adafruit Industries, LLC.
Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180525193623.15533-3-david@lechnology.com

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -8,6 +8,7 @@ abracon	Abracon Corporation
 actions	Actions Semiconductor Co., Ltd.
 active-semi	Active-Semi International Inc
 ad	Avionic Design GmbH
+adafruit	Adafruit Industries, LLC
 adapteva	Adapteva, Inc.
 adaptrum	Adaptrum, Inc.
 adh	AD Holdings Plc.