Finish VLAN_MTU support in nve(4).  The interface appears to be able to handle long frames in its default mode, so setting the respective bit in if_capenable is enough.
Finish VLAN_MTU support in nve(4).  The interface appears to be able
to handle long frames in its default mode, so setting the respective
bit in if_capenable is enough.

Tested by:	yongari

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase