netdev-vport: Use vport set_stats instead of internal dev.

netdev-vport: Use vport set_stats instead of internal dev.

In certain cases we require the ability to provide stats that are
added to the values collected by the kernel (currently only used
by bond fake devices).  Internal devices previously implemented
this directly but now that their stats are now handled by the vport
layer the functionality has been moved there.  This removes the
userspace code to set the stats and replaces it with a mechanism
to access the equivalent functionality in the vport layer.