pvh: disable 32-bit guest support for now

pvh: disable 32-bit guest support for now

Removing the assert allows the PVH code to call this during vmcs
construction in a later patch, making the code more robust by removing
duplicate code.

To be implemented.

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>
Acked-by: Tim Deegan <tim@xen.org>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: Eddie Dong <eddie.dong@intel.com>