x86: Kill all traces of irq_remapping_get_irq_domain()

All users are converted to use the fwspec based parent domain lookup.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201024213535.443185-30-dwmw2@infradead.org