Altera hardware mutex
Altera hardware mutex can provide hardware assistance for synchronization and
mutual exclusion between processors in asymmetric/symmetric multiprocessing
(AMP/SMP) system or multi processes/threads in uniprocessor system.

Required properties:
- compatible : "altr,mutex-1.0".
- reg : physical base address of the mutex and length of memory mapped
     region.

Example:
	mutex0: mutex0@0x100 {
		compatible = "altr,hwmutex-1.0";
		reg = <0x100 0x8>;
	};

Example of mutex's client node that includes mutex phandle.
	mclient0: mclient0@0x200 {
		compatible = "client-1.0";
		reg = <0x200 0x10>;
		mutex = <&mutex0>;
	};
