dt: Add vendor prefix for Sensirion

Sensirion is a sensor manufacturer, providing relative humidity sensors,
temperature sensor and flow sensor solutions.
Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -265,6 +265,7 @@ sbs	Smart Battery System
 schindler	Schindler
 seagate	Seagate Technology PLC
 semtech	Semtech Corporation
+sensirion	Sensirion AG
 sgx	SGX Sensortech
 sharp	Sharp Corporation
 si-en	Si-En Technology Ltd.