ENH: Added func __generate_bhyve_custom_pci_string
ENH: Added func __generate_bhyve_custom_pci_string

Added function __generate_bhyve_custom_pci_string to generate bhyve
command string for custom PCI devices as set by chyves properties
starting withe “pcidev:”, see man page for more information under
Manually Setting Properties.

For PCI passthrough device: each virtual PCI device sharing a slot on
the host must also use the same slot for the guest. Otherwise each
device is assigned it’s own PCI slot.

This expands a great deal on the simple __get_zfs_pcidev_conf()
function.

chyves/chyves