dt-bindings: Add Y Soft Corporation vendor prefix

Y Soft is headquartered in the Czech Republic and it is a worldwide
provider of enterprise office solutions for print management.
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -414,6 +414,7 @@ xes	Extreme Engineering Solutions (X-ES)
 xillybus	Xillybus Ltd.
 xlnx	Xilinx
 xunlong	Shenzhen Xunlong Software CO.,Limited
+ysoft	Y Soft Corporation a.s.
 zarlink	Zarlink Semiconductor
 zeitec	ZEITEC Semiconductor Co., LTD.
 zidoo	Shenzhen Zidoo Technology Co., Ltd.