net/hyperv: Fix data corruption in rndis_filter_receive()

Limiting the memcpy to be the sizeof(struct rndis_message) can truncate
the message if there are Per-Packet-Info or Out-of-Band data.

In my earlier patch (commit 45326342

), the unnecessary kmap_atomic and
kunmap_atomic surrounding this memcpy have been removed because the memory
in the receive buffer is always mapped. This memcpy is not necessary
either. To fix the bug, I removed the memcpy.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>