own entry in the softc. This should allow more of cbb_pci_intr() to
migrate to a new cbb_pci_filt() so that we don't have to run cbb's ISR
in almost every case we get an interrupt. We can't just move
cbb_pci_intr into cbb_pci_filt because it does things that aren't safe
to do from a fast interrupt handler, err I mean from a filter. This is
an important first step.
# I wonder if I need to make cardok volatile or not.
6e878bc765