x86/EFI: properly handle run time memory regions outside the 1:1 map

x86/EFI: properly handle run time memory regions outside the 1:1 map

Namely with PFN compression, MMIO ranges that the firmware may need
runtime access to can live in the holes that gets shrunk/eliminated by
PFN compression, and hence no mappings would result from simply
copying Xen's direct mapping table's L3 page table entries. Build
mappings for this "manually" in the EFI runtime call 1:1 page tables.

Use the opportunity to also properly identify (via a forcibly undefined
manifest constant) all the disabled code regions associated with it not
being acceptable for us to call SetVirtualAddressMap().

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