FROMLIST: genirq: Add __irq_modify_status() helper to clear/set special flags

Some arch-specific flags need to be set/cleared, but not exposed to
random device drivers. Introduce a new helper (__irq_modify_status())
that takes an arbitrary mask, and rewrite irq_modify_status() to use
this new helper.

No functionnal change.

Bug: 191808738
Link: https://lore.kernel.org/lkml/20201124141449.572446-5-maz@kernel.org/


Change-Id: I2c2c0d6599d0ab39fad22462bf4c87694362fba8
Signed-off-by: Marc Zyngier <maz@kernel.org>
[minor port to 5.10]
Signed-off-by: Stephen Dickey <dickey@codeaurora.org>