x86/shadow: sh_{make,destroy}_monitor_table() are "even more" HVM-only

x86/shadow: sh_{make,destroy}_monitor_table() are "even more" HVM-only

With them depending on just the number of shadow levels, there's no need
for more than one instance of them, and hence no need for any hook (IOW
452219e24648 ["x86/shadow: monitor table is HVM-only"] didn't go quite
far enough). Move the functions to hvm.c while dropping the dead
is_pv_32bit_domain() code paths.

While moving the code, replace a stale comment reference to
sh_install_xen_entries_in_l4(). Doing so made me notice the function
also didn't have its prototype dropped in 8d7b633adab7 ("x86/mm:
Consolidate all Xen L4 slot writing into init_xen_l4_slots()"), which
gets done here as well.

Also make their first parameters const.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>