dt-bindings: add vendor prefix for Insignal Ltd

Add vendor prefix for Insignal Ltd (http://www.insignal.co.kr).
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210504120742.12922-1-krzysztof.kozlowski@canonical.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.yaml

@@ -533,6 +533,8 @@ patternProperties:
     description: Innolux Corporation
   "^inside-secure,.*":
     description: INSIDE Secure
+  "^insignal,.*":
+    description: Insignal Ltd.
   "^inspur,.*":
     description: Inspur Corporation
   "^intel,.*":