powerpc: Switch irq_domain_add_nomap() to use fwnode

powerpc: Switch irq_domain_add_nomap() to use fwnode

All irq_domain_add_*() functions are going away. PowerPC is the only
user of irq_domain_add_nomap() and there is no irq_domain_create_nomap()
complement.

Therefore, to align with the rest of the kernel, rename
irq_domain_add_nomap() to irq_domain_create_nomap() and accept a
fwnode_handle instead of a device_node.

[ tglx: Fix up subject prefix ]

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250319092951.37667-40-jirislaby@kernel.org