guest/pvh: special case the low 1MB

guest/pvh: special case the low 1MB

When running as a PVH guest Xen only special cases the trampoline
code in the low 1MB, without also reserving the space used by the
relocated metadata or the trampoline stack.

Fix this by always reserving the low 1MB regardless of whether Xen is
running as a guest or natively.

Reported-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>