ARM: dts: Add vendor prefix for Grinn

Grinn is a company located in Poland, Europe producing
System on Modules.
Webpage: http://www.grinn-global.com/Signed-off-by: Rostislav Lisovy <lisovy@jablotron.cz>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -77,6 +77,7 @@ giantplus	Giantplus Technology Co., Ltd.
 globalscale	Globalscale Technologies, Inc.
 gmt	Global Mixed-mode Technology, Inc.
 google	Google, Inc.
+grinn	Grinn
 gumstix	Gumstix, Inc.
 gw	Gateworks Corporation
 hannstar	HannStar Display Corporation