xen: arm: define guest virtual platform in API headers

xen: arm: define guest virtual platform in API headers

The tools and the hypervisor need to agree on various aspects of the guest
environment, such as interrupt numbers, memory layout, initial register values
for registers which are implementation defined etc. Therefore move the
associated defines into the public interface headers, or create them as
necessary.

This just exposes the current de-facto standard guest layout, which may be
subject to change in the future. This deliberately does not make the guest
layout dynamic since there is currently no need.

These values should not be exposed to guests, they should find these things
out via device tree or should not be relying on implementation defined
defaults.

Various bits of the hypervisor needed to change to configure dom0 with the real
platform values while using the virtual platform configuration for guests.
Arrange for this where appropriate and plumb through as needed.

We also need to expose some 64-bit values (e.g. PSR_GUEST64_INIT) for the
benefit of 32 bit toolstacks building 64 bit guests.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>