hvf: arm: Implement PSCI handling

hvf: arm: Implement PSCI handling

We need to handle PSCI calls. Most of the TCG code works for us,
but we can simplify it to only handle aa64 mode and we need to
handle SUSPEND differently.

This patch takes the TCG code as template and duplicates it in HVF.

To tell the guest that we support PSCI 0.2 now, update the check in
arm_cpu_initfn() as well.

Signed-off-by: Alexander Graf <agraf@csgraf.de>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20210916155404.86958-8-agraf@csgraf.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>