genirq: Remove unused remove_percpu_irq()

remove_percpu_irq() has been unused since it was added in 2011 by
commit 31d9d9b6 ("genirq: Add support for per-cpu dev_id interrupts")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250420164656.112641-1-linux@treblig.org