x86/altp2m: add control of suppress_ve

x86/altp2m: add control of suppress_ve

The existing ept_set_entry() and ept_get_entry() routines are extended
to optionally set/get suppress_ve.  Passing -1 will set suppress_ve on
new p2m entries, or retain suppress_ve flag on existing entries.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
Signed-off-by: Ravi Sahita <ravi.sahita@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
Also adjust the caller in set_identity_p2m_entry().

Signed-off-by: Jan Beulich <jbeulich@suse.com>