* 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 be one of following:
	  "syscon",
	  "sprd,ums9230-glbregs".
- 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.
- #syscon-cells:   Represents the number of args. Used when syscon-names
  is going to be used. The value is vendor specific.

Examples:
gpr: iomuxc-gpr@020e0000 {
	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
	reg = <0x020e0000 0x38>;
	hwlocks = <&hwlock1 1>;
};

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


==Syscon names==

Refer to syscon node by names with phandle args in syscon consumer node.

Required properties:
- syscons:	List of phandle and any number of args. Args is specific to
		differnet vendor. For example: In Spreatrum SoCs, the 1st arg
		will be treated as register address offset and the 2nd is bit
		mask as default.

- syscon-names:	List of syscon node name strings sorted in the same
		order as the syscons property.

Optional properties:

- syscon-ranges:	/*TODO*/


For example:

apb_regs: syscon@20008000 {
	compatible = "sprd,apb-glb", "syscon";
	#syscon-cells = <2>;
	reg = <0x20008000 0x100>;
};

aon_regs: syscon@40008000 {
	compatible = "sprd,aon-glb", "syscon";
	#syscon-cells = <1>;
	reg = <0x40008000 0x100>;
};

display@40500000 {
	...
	syscons = <&ap_apb_regs 0x4 0xf00>, <&aon_regs 0x8>;
	syscon-names = "enable", "power";
};
