hyperv/hn: remove the MTU and IFF_DRV_RUNNING checking in hn_rxpkt()

[decui_microsoft.com]

Summary

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.

[sepherosa_gmail.com]

ship it