libxc: set flag for support of linear p2m list in domain builder

libxc: set flag for support of linear p2m list in domain builder

Set the SIF_VIRT_P2M_4TOOLS flag for pv-domUs in the domain builder
to indicate the Xen tools have full support for the virtual mapped
linear p2m list.

This will enable pv-domUs to drop support of the 3 level p2m tree
and use the linear list only. Without setting this flag some kernels
might limit themselves to 512 GB memory size in order not to break
migration.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>