KVM: arm64: Simplify userspace notification of interrupt state

KVM: arm64: Simplify userspace notification of interrupt state

The userspace notification of interrupts is has a few problems:

- it is utterly pointless

- it is annoyingly split between detecting the need for notification
  and the population of the interrupts in the run structure

We can't do anything about the former (yet), but the latter can be
addressed. If we detect that we must notify userspace, we know that
we are going to exit, as we populate the exit status. Which means
we can also populate the interrupt state at this stage and be done
with it.

This simplifies the structure of the code.

Reviewed-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/20260520100200.543845-3-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>