net: hv_netvsc: reject RSS hash key programming without RX indirection table

In the Linux kernel, the following vulnerability has been resolved: net: hv_netvsc: reject RSS hash key programming without RX indirection table RSS configuration requires a valid RX indirection table. When the device reports a single receive queue, rndis_filter_device_add() does not allocate an indirection table, accepting RSS hash key updates in this state leads to a hang. Fix this by gating netvsc_set_rxfh() on ndc->rx_table_sz and return -EOPNOTSUPP when the table is absent. This aligns set_rxfh with the device capabilities and prevents incorrect behavior.