Nuvoton NPCM Reset controller

Required properties:
- compatible : "nuvoton,npcm750-reset" for NPCM7XX BMC
- reg : specifies physical base address and size of the register.
- #reset-cells: must be set to 2

Optional property:
- nuvoton,sw-reset-number - Contains the software reset number to restart the SoC.
  NPCM7xx contain four software reset that represent numbers 1 to 4.

  If 'nuvoton,sw-reset-number' is not specified software reset is disabled.

Example:
	rstc: rstc@f0801000 {
		compatible = "nuvoton,npcm750-reset";
		reg = <0xf0801000 0x70>;
		#reset-cells = <2>;
		nuvoton,sw-reset-number = <2>;
	};

Specifying reset lines connected to IP NPCM7XX modules
======================================================
example:

        spi0: spi@..... {
                ...
                resets = <&rstc NPCM7XX_RESET_IPSRST2 NPCM7XX_RESET_PSPI1>;
                ...
        };

The index could be found in <dt-bindings/reset/nuvoton,npcm7xx-reset.h>.
