pvh: use PV e820

pvh: use PV e820

Allow PV e820 map to be set and read from a PVH domain.  This requires
moving the pv e820 struct out from the pv-specific domain struct and
into the arch domain struct.

Signed-off-by: Mukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: Eddie Dong <eddie.dong@intel.com>