Samsung Sensorhub driver

Sensorhub is a MCU which manages several sensors and also plays the role
of a virtual sensor device.

Required properties:
- compatible: "samsung,sensorhub-rinato" or "samsung,sensorhub-thermostat"
- spi-max-frequency: max SPI clock frequency
- interrupts: communication interrupt
- ap-mcu-gpios: [out] ap to sensorhub line - used during communication
- mcu-ap-gpios: [in] sensorhub to ap - used during communication
- mcu-reset-gpios: [out] sensorhub reset

Example:

	shub_spi: shub {
		compatible = "samsung,sensorhub-rinato";
		spi-max-frequency = <5000000>;
		interrupt-parent = <&gpx0>;
		interrupts = <2 0>;
		ap-mcu-gpios = <&gpx0 0 0>;
		mcu-ap-gpios = <&gpx0 4 0>;
		mcu-reset-gpios = <&gpx0 5 0>;
	};