of/vendor-prefixes: add Imagination Technologies

The "powervr" prefix which is currently described as "Imagination
Technologies" isn't really appropriate for non-PowerVR hardware, so
deprecate it, changing the description of "powervr" to "PowerVR
(deprecated, use img)", and add a separate "img" prefix for "Imagination
Technologies Ltd.".
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -26,6 +26,7 @@ gef	GE Fanuc Intelligent Platforms Embedded Systems, Inc.
 hp	Hewlett Packard
 ibm	International Business Machines (IBM)
 idt	Integrated Device Technologies, Inc.
+img	Imagination Technologies Ltd.
 intercontrol	Inter Control Group
 linux	Linux-specific binding
 marvell	Marvell Technology Group Ltd.
@@ -37,7 +38,7 @@ nvidia	NVIDIA
 nxp	NXP Semiconductors
 onnn	ON Semiconductor Corp.
 picochip	Picochip Ltd
-powervr	Imagination Technologies
+powervr	PowerVR (deprecated, use img)
 qcom	Qualcomm, Inc.
 ramtron	Ramtron International
 realtek Realtek Semiconductor Corp.