hvf: non-RAM, non-ROMD memory ranges are now correctly mapped in

hvf: non-RAM, non-ROMD memory ranges are now correctly mapped in

If an area is non-RAM and non-ROMD, then remove mappings so accesses
will trap and can be emulated.  Change hvf_find_overlap_slot() to take
a size instead of an end address: it wouldn't return a slot because
callers would pass the same address for start and end.  Don't always
map area as read/write/execute, respect area flags.

Signed-off-by: Cameron Esfahani <dirty@apple.com>
Message-Id: <1d8476c8f86959273fbdf23c86f8b4b611f5e2e1.1574625592.git.dirty@apple.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>