dt-binding: add vendor prefix for SolidRun

SolidRun is a company from Israel producing small-sized home-media
computers like the Marvell Dove based CuBox and Freescale IMX based
CuBox-i. Document the missing vendor prefix.

Signed-off-by: Sebastian Hesselbarth <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Jason Cooper <[e-mail]>

Documentation/devicetree/bindings/vendor-prefixes.txt

···
 sirf	SiRF Technology, Inc.
 smsc	Standard Microsystems Corporation
 snps 	Synopsys, Inc.
+solidrun	SolidRun
 spansion	Spansion Inc.
 st	STMicroelectronics
 ste	ST-Ericsson