We have to set the ISAPNP register index when setting an IRQ via the sysfs
interface.  We already do it for IO, MEM, and DMA resources; I just missed the
IRQ one.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>