irqchip/apple-aic: Skip unnecessary enabling of use_fast_ipi

use_fast_ipi is true by default and there is no need to "enable" it.

Signed-off-by: Nick Chan <towinchenmi@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/all/20240901034143.12731-3-towinchenmi@gmail.com