net/hyperv: Remove the unnecessary memset in rndis_filter_send()

The memory has been allocated by kzalloc, so it's unnecessary to memset
again.

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