Replace all register_ioport_*() with a MemoryRegion.
This permits to use the new Memory stuff like listeners.

For more flexibility, the IO address space is passed as an argument.
Signed-off-by: NJulien Grall <julien.grall@citrix.com>
Acked-by: NAvi Kivity <avi@redhat.com>
[AF: Rebased onto serial split]
Signed-off-by: NAndreas Färber <afaerber@suse.de>