modules: Add kmod-igbvf kernel module for Intel(R) 82576 Virtual Function Ethernet adapters

Intel(R) 82576 is an adapter which supports SR-IOV. Thus the host can
assign Virtual Functions (VFs) to different VMs by the PCI-E Passthrough
(e.g. VFIO for KVM), to gain different advantages (performance, VF to VF
communications, host kernel offload, etc.).

The driver of the passthroughed VFs is the igbvf (igb is NOT
compatible).

This is essential for VM guests, to enable them to utilize this feature.

Signed-off-by: Ye Tao <tydus@hongo.wide.ad.jp>