dt-bindings: Add vendor prefix for ilitek

This adds the vendor prefix ilitek for ILI Technology Corporation (ILITEK).

This prefix is already used several places and I will be adding more.
Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1511122328-31133-2-git-send-email-david@lechnology.com

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -150,6 +150,7 @@ i2se	I2SE GmbH
 ibm	International Business Machines (IBM)
 idt	Integrated Device Technologies, Inc.
 ifi	Ingenieurburo Fur Ic-Technologie (I/F/I)
+ilitek	ILI Technology Corporation (ILITEK)
 img	Imagination Technologies Ltd.
 infineon Infineon Technologies
 inforce	Inforce Computing