nested SVM: adjust guest handling of structure mappings

nested SVM: adjust guest handling of structure mappings

For one, nestedsvm_vmcb_map() error checking must not consist of using
assertions: Global (permanent) mappings can fail, and hence failure
needs to be dealt with properly. And non-global (transient) mappings
can't fail anyway.

And then the I/O port access bitmap handling was broken: It checked
only to first of the accessed ports rather than each of them.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Christoph Egger <chegger@amazon.de>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>