spi: mt65xx: Use IRQF_ONESHOT with threaded IRQ

spi: mt65xx: Use IRQF_ONESHOT with threaded IRQ

This driver is migrated to use threaded IRQ since commit 5972eb05ca32
("spi: spi-mt65xx: Use threaded interrupt for non-SPIMEM transfer"), and
we almost always want to disable the interrupt line to avoid excess
interrupts while the threaded handler is processing SPI transfer.
Use IRQF_ONESHOT for that purpose.

In practice, we see MediaTek devices show SPI transfer timeout errors
when communicating with ChromeOS EC in certain scenarios, and with
IRQF_ONESHOT, the issue goes away.

Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://patch.msgid.link/20251217101131.1975131-1-fshao@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>