memory: hmp: add "-f" for "info mtree"

memory: hmp: add "-f" for "info mtree"

Adding one more option "-f" for "info mtree" to dump the flat views of
all the address spaces.

This will be useful to debug the memory rendering logic, also it'll be
much easier with it to know what memory region is handling what address
range.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <1484556005-29701-3-git-send-email-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>