GitLab

Introduce a helper which decides if a given pfn type has data
in the migration stream.

No change in behaviour intended, except for invalid page types which now
have a safer default.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>