Prepare Intel 82374 emulation for use by Intel 82378 PCI->ISA bridge.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>

Confine to CONFIG_I82374. Add VMState.

Signed-off-by: Andreas Färber <andreas.faerber@web.de>
Reviewed-by: Alexander Graf <agraf@suse.de>