irqchip/ls-scfg-msi: Fix MSI affinity handling

irqchip/ls-scfg-msi: Fix MSI affinity handling

The ls-scfs-msi driver is not dealing with the effective affinity
as it should. Let's fix that, and make it clear that the effective
affinity is restricted to a single CPU. Also prevent the driver from
messing with the internals of the affinity setting infrastructure.

Reported-by: Alexandre Belloni <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Alexandre Belloni <[email protected]>
Cc: Jason Cooper <[email protected]>
Cc: Yang Yingliang <[email protected]>
Cc: Sumit Garg <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]