pci_find_bsf
dev = pci_find_bsf(0, 0, 0);
device_t pci_find_bsf(uint8_t, uint8_t, uint8_t);
smb_dev = pci_find_bsf(0, 20, 0);
smb_dev = pci_find_bsf(0, 20, 0);
mcp55 = pci_find_bsf(0, 0, 0);