cxgb4: silence shift wrapping static checker warning

I don't know how large "tp->vlan_shift" is but static checkers worry
about shift wrapping bugs here.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NDimitris Michailidis <dm@chelsio.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/l2t.c

@@ -423,7 +423,7 @@ u64 cxgb4_select_ntuple(struct net_device *dev,
 	 * in the Compressed Filter Tuple.
 	 */
 	if (tp->vlan_shift >= 0 && l2t->vlan != VLAN_NONE)
-		ntuple |= (F_FT_VLAN_VLD | l2t->vlan) << tp->vlan_shift;
+		ntuple |= (u64)(F_FT_VLAN_VLD | l2t->vlan) << tp->vlan_shift;
 
 	if (tp->port_shift >= 0)
 		ntuple |= (u64)l2t->lport << tp->port_shift;