It's unnecessary because the upper nework stack does the same checking.
In the case of Hyper-V SR-IOV, we need to remove the checking because
1) multicast/broadcast packets are still received through the synthetic
NIC and we need to inject the packets through the VF interface;
2) we must inject the packets even if the synthetic NIC is down, or has
a different MTU from the VF device.
Reviewed by: sephe
Approved by: sephe (mentor)
MFC after: 2 weeks
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D8962
c927d68136