dt-bindings: add SFF vendor prefix

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -289,6 +289,7 @@ schindler	Schindler
 seagate	Seagate Technology PLC
 semtech	Semtech Corporation
 sensirion	Sensirion AG
+sff	Small Form Factor Committee
 sgx	SGX Sensortech
 sharp	Sharp Corporation
 si-en	Si-En Technology Ltd.