Runtime services may (and do) use device mappings on some UEFI implementations.

Runtime services may (and do) use device mappings on some UEFI implementations.
Skip these mappings during the remap-pahse as they are likely to be in
a different 512G bloch as memory and SetVirtualAddressMap() shouldn't need
them.  But do assign a new virtual address and let efi(4) create a mapping.
Add a PMAP_DEVICE flag such that pmap_enter() can continue to be used
to create these mappings.

ok patrick@