ethtool: Fix set RXNFC command with symmetric RSS hash

The sanity check that both source and destination are set when symmetric
RSS hash is requested is only relevant for ETHTOOL_SRXFH (rx-flow-hash),
it should not be performed on any other commands (e.g.
ETHTOOL_SRXCLSRLINS/ETHTOOL_SRXCLSRLDEL).

This resolves accessing uninitialized 'info.data' field, and fixes false
errors in rule insertion:
  # ethtool --config-ntuple eth2 flow-type ip4 dst-ip 255.255.255.255 action -1 loc 0
  rmgr: Cannot insert RX class rule: Invalid argument
  Cannot insert classification rule

Fixes: 13e5934 ("net: ethtool: add support for symmetric-xor RSS hash")
Cc: Ahmed Zaki <ahmed.zaki@intel.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Reviewed-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Ahmed Zaki <ahmed.zaki@intel.com>
Link: https://patch.msgid.link/20250126191845.316589-1-gal@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/ethtool/ioctl.c

@@ -998,7 +998,7 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
 	    ethtool_get_flow_spec_ring(info.fs.ring_cookie))
 		return -EINVAL;
 
-	if (ops->get_rxfh) {
+	if (cmd == ETHTOOL_SRXFH && ops->get_rxfh) {
 		struct ethtool_rxfh_param rxfh = {};
 
 		rc = ops->get_rxfh(dev, &rxfh);