irqdomain: Introduce irq_domain_create_legacy() API

Introduce irq_domain_create_legacy() API which is functional equivalent
to the existing irq_domain_add_legacy(), but takes a pointer to the struct
fwnode_handle as a parameter.

This is useful for non OF systems.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20201030165919.86234-5-andriy.shevchenko@linux.intel.com