kexec: add more pages to v1 environment

kexec: add more pages to v1 environment

Destination pages need mappings to be added to the page tables in the
v1 case (where nothing else calls machine_kexec_add_page() for them).

Further, without the tools mapping the low 1Mb (expected by at least
some Linux version), we need to do so in the hypervisor in the v1 case.

Suggested-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Alan Robinson <alan.robinson@ts.fujitsu.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>