hw/char/serial-isa: Implement relocation and enabling/disabling for TYPE_ISA_SERIAL

hw/char/serial-isa: Implement relocation and enabling/disabling for TYPE_ISA_SERIAL

The real SuperI/O chips emulated by QEMU allow for relocating and enabling or
disabling their SuperI/O functions via software. So far this is not implemented.
Prepare for that by adding isa_serial_set_{enabled,iobase}.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20240114123911.4877-9-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>