devicetree: bindings: add Zarlink to the vendor prefixes

Even though the company belongs to Microsemi, many chips are still
labeled as Zarlink. Among them is the family of network clock generators,
the zl3034x.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -135,3 +135,4 @@ wm	Wondermedia Technologies, Inc.
 xes	Extreme Engineering Solutions (X-ES)
 xlnx	Xilinx
 zyxel	ZyXEL Communications Corp.
+zarlink	Zarlink Semiconductor