* Devantech SRF04 ultrasonic range finder
  Bit-banging driver using two GPIOs

Required properties:
 - compatible:	Should be "devantech,srf04"

 - trig-gpios:	Definition of the GPIO for the triggering (output)
		This GPIO is set for about 10 us by the driver to tell the
		device it should initiate the measurement cycle.

 - echo-gpios:	Definition of the GPIO for the echo (input)
		This GPIO is set by the device as soon as an ultrasonic
		burst is sent out and reset when the first echo is
		received.
		Thus this GPIO is set while the ultrasonic waves are doing
		one round trip.
		It needs to be an GPIO which is able to deliver an
		interrupt because the time between two interrupts is
		measured in the driver.
		See Documentation/devicetree/bindings/gpio/gpio.txt for
		information on how to specify a consumer gpio.

Example:
srf04@0 {
	compatible = "devantech,srf04";
	trig-gpios = <&gpio1 15 GPIO_ACTIVE_HIGH>;
	echo-gpios = <&gpio2  6 GPIO_ACTIVE_HIGH>;
};