firewire: ohci: replace request_irq() with request_threaded_irq()

Nowadays request_irq() is a wrapper of request_threaded_irq(). The IRQ
handler of 1394 ohci driver has never been optimized yet, while it is
a good preparation for the future work to replace the latter.

This commit replaces the former.

Link: https://lore.kernel.org/r/20240331135037.191479-3-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>