net/mlx5e: TLS, Read capabilities only when it is safe

Read TLS caps from the core driver only when TLS is supported, i.e
mlx5_accel_is_tls_device returns true.

Fixes: 790af90c ("net/mlx5e: TLS, build TLS netdev from capabilities")
Change-Id: I5f21ff4d684901af487e366a7e0cf032b54ee9cf
Reported-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Boris Pismenny <borisp@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_accel/tls.c

@@ -183,12 +183,13 @@ static const struct tlsdev_ops mlx5e_tls_ops = {
 
 void mlx5e_tls_build_netdev(struct mlx5e_priv *priv)
 {
-	u32 caps = mlx5_accel_tls_device_caps(priv->mdev);
 	struct net_device *netdev = priv->netdev;
+	u32 caps;
 
 	if (!mlx5_accel_is_tls_device(priv->mdev))
 		return;
 
+	caps = mlx5_accel_tls_device_caps(priv->mdev);
 	if (caps & MLX5_ACCEL_TLS_TX) {
 		netdev->features          |= NETIF_F_HW_TLS_TX;
 		netdev->hw_features       |= NETIF_F_HW_TLS_TX;