powerpc/4xx: Add optional "reset_type" property to control reboot via dts

Reboot property to control system reboot on PPC4xx systems:

By setting "reset_type" to one of the following values, the default

software reset mechanism may be overidden. Here the possible values of

"reset_type":

      1 - PPC4xx core reset

      2 - PPC4xx chip reset

      3 - PPC4xx system reset (default)

Example:

		cpu@0 {

			device_type = "cpu";

			model = "PowerPC,440SPe";

			...

			reset-type = <2>;	/* Use chip-reset */

		};

arch_initcall(ppc4xx_l2c_probe);

/*

 * At present, this routine just applies a system reset.

 * Apply a system reset. Alternatively a board specific value may be

 * provided via the "reset-type" property in the cpu node.

 */

void ppc4xx_reset_system(char *cmd)

{

	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_RST_SYSTEM);

	struct device_node *np;

	u32 reset_type = DBCR0_RST_SYSTEM;

	const u32 *prop;

	np = of_find_node_by_type(NULL, "cpu");

	if (np) {

		prop = of_get_property(np, "reset-type", NULL);

		/*

		 * Check if property exists and if it is in range:

		 * 1 - PPC4xx core reset

		 * 2 - PPC4xx chip reset

		 * 3 - PPC4xx system reset (default)

		 */

		if ((prop) && ((prop[0] >= 1) && (prop[0] <= 3)))

			reset_type = prop[0] << 28;

	}

	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | reset_type);

	while (1)

		;	/* Just in case the reset doesn't work */

}