* System Controller Registers R/W driver

System controller node represents a register region containing a set
of miscellaneous registers. The registers are not cohesive enough to
represent as any specific type of device. The typical use-case is for
some other node's driver, or platform-specific code, to acquire a
reference to the syscon node (e.g. by phandle, node path, or search
using a specific compatible value), interrogate the node (or associated
OS driver) to determine the location of the registers, and access the
registers directly.

Required properties:
- compatible: Should contain "syscon".
- reg: the register region can be accessed from syscon

Optional property:
- reg-io-width: the size (in bytes) of the IO accesses that should be
  performed on the device.
- hwlocks: reference to a phandle of a hardware spinlock provider node.

Examples:
gpr: iomuxc-gpr@20e0000 {
	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
	reg = <0x020e0000 0x38>;
	hwlocks = <&hwlock1 1>;
};

hwlock1: hwspinlock@40500000 {
	...
	reg = <0x40500000 0x1000>;
	#hwlock-cells = <1>;
};
