VSOCK: vmci - fix possible info leak in vmci_transport_dgram_dequeue()

In case we received no data on the call to skb_recv_datagram(), i.e.
skb->data is NULL, vmci_transport_dgram_dequeue() will return with 0
without updating msg_namelen leading to net/socket.c leaking the local,
uninitialized sockaddr_storage variable to userland -- 128 bytes of
kernel stack memory.

Fix this by moving the already existing msg_namelen assignment a few
lines above.

Cc: Andy King <acking@vmware.com>
Cc: Dmitry Torokhov <dtor@vmware.com>
Cc: George Zhang <georgezhang@vmware.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
int vmci_transport_send_read_bh(struct sockaddr_vm *dst,
				struct sockaddr_vm *src)
{
	return vmci_transport_send_control_pkt_bh(
					dst, src,
					VMCI_TRANSPORT_PACKET_TYPE_READ, 0,
					0, NULL, VMCI_INVALID_HANDLE);
}

int vmci_transport_send_read_bh(struct sockaddr_vm *dst,
				struct sockaddr_vm *src)
{
	return vmci_transport_send_control_pkt_bh(
					dst, src,
					VMCI_TRANSPORT_PACKET_TYPE_READ, 0,
					0, NULL, VMCI_INVALID_HANDLE);
}
