irqdomain: Use irq_domain_instantiate()'s return value as initializers

irqdomain: Use irq_domain_instantiate()'s return value as initializers

This makes the code more compact.

Note that irq_domain_create_hierarchy()'s handling of size is now part of
info's initializer (using the ternary operator). That makes more sense
while reading it.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250319092951.37667-51-jirislaby@kernel.org