Some of the VIA pm and propm devices are actually the same device as the

Some of the VIA pm and propm devices are actually the same device as the
PCI-ISA bridge.  Thus, when viapm0 or viapropm0 attaches, isab0 dosen't
attach so there is no isa0 bus hung off of that bridge.  In the non-ACPI
case, legacy0 will add an isa0 anyway as a fail-safe, but ACPI assumes that
any ISA bus will be enumerated via a bridge.  To fix this, call
isab_attach() to attach an isa0 ISA child bus device if the pm or propm
device we are probing is a PCI-ISA bridge.  Both drivers now have to
implement the bus_if interface via the generic methods for resource
allocation, etc. to work.  Also, we now add 2 new ISA bus drivers that
attach to viapm and viapropm devices.

PR:		kern/87363
Reported by:	Oliver Fromme olli at secnetix dot de
Tested by:	glebius
MFC after:	1 week