dts: bindings: Add vendor prefix festo

Add vendor prefix for Festo SE & Co. KG

Signed-off-by: Jeppe Odgaard <jeppe.odgaard@prevas.dk>

Author: Jeppe Odgaard

dts/bindings/vendor-prefixes.txt

@@ -232,6 +232,7 @@ fastrax	Fastrax Oy
 fcs	Fairchild Semiconductor
 feixin	Shenzhen Feixin Photoelectic Co., Ltd
 feiyang	Shenzhen Fly Young Technology Co.,LTD.
+festo	Festo SE & Co. KG
 fii	Foxconn Industrial Internet
 fintek	Feature Integration Technology Inc.
 firefly	Firefly