dt-bindings: vendor-prefixes: add Sipeed

Shenzhen Sipeed Technology Co., Ltd. is a company focused on development
kits, which also contains rebranded Lichee Pi series.

Add its vendor prefix binding.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.yaml

@@ -839,6 +839,8 @@ patternProperties:
     description: Sinlinx Electronics Technology Co., LTD
   "^sinovoip,.*":
     description: SinoVoip Co., Ltd
+  "^sipeed,.*":
+    description: Shenzhen Sipeed Technology Co., Ltd.
   "^sirf,.*":
     description: SiRF Technology, Inc.
   "^sis,.*":