Again... (after 07dc7880 and 9157eee1).

We now extract the ISA bus specific helpers.
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180308223946.26784-2-f4bug@amsat.org>
Reviewed-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>