Create VM_MEMATTR_DEVICE on all architectures

This is intended to be used with memory mapped IO, e.g. from
bus_space_map with no flags, or pmap_mapdev.

Use this new memory type in the map request configured by
resource_init_map_request, and in pciconf.

Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D29692