amd64: provide PHYS_IN_DMAP() and VIRT_IN_DMAP()

It is useful for quickly checking an address against the DMAP region.
These definitions exist already on arm64 and riscv.

Reviewed by: kib, markj
MFC after: 3 days
Sponsored by: Juniper Networks, Inc.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D32962

(cherry picked from commit 90d4da62259299a8d91fed1121be97ac5b7b6b3c)