Only change DMAP props on DMAP covered memory

When changing memory properties in the arm64 pmap we need to keep both
the kernel address and DMAP mappings in sync.

To keep the kernel and DMAP memory in sync we recurse when updating the
former to also update the latter. There was insuffucuent checking around
this recursion. It would check if the virtual address is not within the
DMAP region, but not if the physical address is covered.

Add the missing check as without it the recursion may return an error.

Sponsored by: The FreeBSD Foundation