udev: net_id: Improve predictable names for SR-IOV virtual devices

udev: net_id: Improve predictable names for SR-IOV virtual devices

With PCI SR-IOV, a number of virtual network devices can be enabled,
all of which share the same physical network device.  Currently,
udev generates names for SR-IOV virtual functions as if they were
independent network devices.

With this change, the predictable network device naming code will
check if a network device is an SR-IOV virtual device, and will
generate a name based on the physical PCI device plus a "v%u"
suffix.  This should improve readability and predictability of
device names.

Here is an example of how this change would affect naming:

before patch  |  after patch
-----------------------------
eno1          |  eno1          onboard NIC, physical function
enp101s0f0    |  eno1v0        onboard NIC, SR-IOV virtual func 0
enp101s0f1    |  eno1v1        onboard NIC, SR-IOV virtual func 1