amd64 pmap: preset A and M bits for pmap_qenter() and pmap_kenter() mappings

This removes one or two atomic update of the pte on access. Also it
makes the pte constant during its lifecycle.

Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D33778