KVM: arm64: GICv3: Preserve EOIcount on exit

KVM: arm64: GICv3: Preserve EOIcount on exit

EOIcount is how the virtual CPU interface signals that the guest
is deactivating interrupts outside of the LRs when EOImode==0.

We therefore need to preserve that information so that we can find
out what actually needs deactivating.

Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://msgid.link/20251120172540.2267180-12-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>