of: add vendor prefix for GMT

Adding Global Mixed-mode Technology Inc. to the list
of devicetree vendor prefixes.

Signed-off-by: Wei Ni <wni@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -32,6 +32,7 @@ est	ESTeem Wireless Modems
 fsl	Freescale Semiconductor
 GEFanuc	GE Fanuc Intelligent Platforms Embedded Systems, Inc.
 gef	GE Fanuc Intelligent Platforms Embedded Systems, Inc.
+gmt	Global Mixed-mode Technology, Inc.
 hisilicon	Hisilicon Limited.
 hp	Hewlett Packard
 ibm	International Business Machines (IBM)