hv_netvsc: Fix extra rcu_read_unlock in netvsc_recv_callback()

There is an extra rcu_read_unlock left in netvsc_recv_callback(),
after a previous patch that removes RCU from this function.
This patch removes the extra RCU unlock.

Fixes: 345ac089 ("hv_netvsc: pass netvsc_device to receive callback")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc_drv.c

@@ -836,7 +836,6 @@ int netvsc_recv_callback(struct net_device *net,
 
 	if (unlikely(!skb)) {
 		++net_device_ctx->eth_stats.rx_no_memory;
-		rcu_read_unlock();
 		return NVSP_STAT_FAIL;
 	}