s390x: virtio machine storage keys

s390x: virtio machine storage keys

For emulation (and migration) we need to know about the guest's storage keys.
These are separate from actual RAM contents, so we need to allocate them in
parallel to RAM.

While touching the file, this patch also adjusts the hypercall function
to a new syntax that aligns better with tcg emulated code.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>