amd64: add pmap_page_set_memattr_noflush()
Similar to pmap_page_set_memattr() by setting MD page cache attribute
to the argument. Unlike pmap_page_set_memattr(), does not flush cache
for the direct mapping of the page.
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D32318