of: Add vendor prefix for Energy Micro

The kernel supports devices with the following compatible strings
already:

	energymicro,efm32-i2c
	energymicro,efm32-uart
	energymicro,efm32-spi
	energymicro,efm32-timer

So add "energymicro" to the list of vendors.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -43,6 +43,7 @@ dmo	Data Modul AG
 ebv	EBV Elektronik
 edt	Emerging Display Technologies
 emmicro	EM Microelectronic
+energymicro	Silicon Laboratories (formerly Energy Micro AS)
 epcos	EPCOS AG
 epfl	Ecole Polytechnique Fédérale de Lausanne
 epson	Seiko Epson Corp.