declance: Remove IRQF_ONESHOT

Passing IRQF_ONESHOT ensures that the interrupt source is masked until
the secondary (threaded) handler is done. If only a primary handler is
used then the flag makes no sense because the interrupt can not fire
(again) while its handler is running.
The flag also disallows force-threading of the primary handler and the
irq-core will warn about this as of commit aef30c8d569c0 ("genirq: Warn
about using IRQF_ONESHOT without a threaded handler").

The IRQF_ONESHOT flag was added in commit 0fabe1021f8bc ("MIPS:
DECstation I/O ASIC DMA interrupt classes"). It moved
clear_ioasic_dma_irq() from the driver into the irq-chip.
For EOI interrupts the clear_ioasic_dma_irq() callback is now invoked as
->irq_eoi() which is invoked after the IRQ was handled while the
interrupt is masked due to IRQF_ONESHOT. Without IRQF_ONESHOT it would
be invoked while interrupt is unmasked (but interrupts are disabled).

If it is *required* to invoke EOI-ack while the interrupt is masked (and
not a misunderstanding) due to irq-chip cascading/ hierarchical reasons
then using handle_fasteoi_mask_irq() as flow-handler would be the right
way to do so.

Remove IRQF_ONESHOT to irqflags.

Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Maciej W. Rozycki <macro@orcam.me.uk>
Link: https://patch.msgid.link/20260127135334.qUEaYP9G@linutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>