fixing EISA with I/O APIC

[Felix Deichmann <m4j0rd0m0%gmail.com@localhost>]

Hi,

could anyone please have a look at PR 47907?
A simple fix is also included.

EISA interrupts on i386 are broken (for a long time now, as it seems) 
when used with I/O APIC, due to "type punning" gone wrong. This should 
for example affect all MP systems with EISA bus.

The fix is just copy&paste from sys/arch/x86/pci/pci_intr_machdep.c, 
where rev. 1.12 deals with the changes required for some struct 
modifications.
It seems EISA was forgotten, unfortunately.

A pull-up would also be great.

Thanks
Felix