hw/arm/virt: allow pmu instantiation with userspace irqchip

Move the in-kernel-irqchip test to only guard the set-irq
stage, not the init stage of the PMU.  Also add the PMU to
the KVM device irq line synchronization to enable its use.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Message-id: 1500471597-2517-4-git-send-email-drjones@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
