dt-bindings: Add Silicon Mitus vendor prefix

Add vendor prefix for Silicon Mitus. Currently there is binding for
sm5502 extcon driver ("siliconmitus,sm5502-muic").

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -145,6 +145,7 @@ schindler	Schindler
 seagate	Seagate Technology PLC
 sil	Silicon Image
 silabs	Silicon Laboratories
+siliconmitus	Silicon Mitus, Inc.
 simtek
 sii	Seiko Instruments, Inc.
 silergy	Silergy Corp.