IB/hfi1: Ensure ucast_dlid access doesnt exceed bounds

The dlid assignment made by looking into the u_ucast_dlid array does not
do an explicit check for the size of the array. The code path to arrive at
def_port, the index value is long and complicated so its best to just have
an explicit check here.

Signed-off-by: Dennis Dalessandro <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/ulp/opa_vnic/opa_vnic_encap.c

···
 			if (unlikely(!dlid))
 				v_warn("Null dlid in MAC address\n");
 		} else if (def_port != OPA_VNIC_INVALID_PORT) {
-			dlid = info->vesw.u_ucast_dlid[def_port];
+			if (def_port < OPA_VESW_MAX_NUM_DEF_PORT)
+				dlid = info->vesw.u_ucast_dlid[def_port];
 		}
 	}