of: add vendor prefixe for EPFL

Using "epfl" for Ecole Polytechnique Fédérale de Lausanne.
Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -27,6 +27,7 @@ dallas	Maxim Integrated Products (formerly Dallas Semiconductor)
 davicom	DAVICOM Semiconductor, Inc.
 denx	Denx Software Engineering
 emmicro	EM Microelectronic
+epfl	Ecole Polytechnique Fédérale de Lausanne
 epson	Seiko Epson Corp.
 est	ESTeem Wireless Modems
 fsl	Freescale Semiconductor