net/mlx5: Fix unused function warning of mlx5i_flow_type_mask

The cited commit is causing unused-function warning[1] when
CONFIG_MLX5_EN_RXNFC is not set.
Fix this by moving the function into the ifdef, where it's only used

[1]
warning: ‘mlx5i_flow_type_mask’ defined but not used [-Wunused-function]

Fixes: 9fbe1c25 ("net/mlx5i: Enable Rx steering for IPoIB via ethtool")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/ipoib/ethtool.c

@@ -33,11 +33,6 @@
 #include "en.h"
 #include "ipoib.h"
 
-static u32 mlx5i_flow_type_mask(u32 flow_type)
-{
-	return flow_type & ~(FLOW_EXT | FLOW_MAC_EXT | FLOW_RSS);
-}
-
 static void mlx5i_get_drvinfo(struct net_device *dev,
 			      struct ethtool_drvinfo *drvinfo)
 {
@@ -223,6 +218,11 @@ static int mlx5i_get_link_ksettings(struct net_device *netdev,
 }
 
 #ifdef CONFIG_MLX5_EN_RXNFC
+static u32 mlx5i_flow_type_mask(u32 flow_type)
+{
+	return flow_type & ~(FLOW_EXT | FLOW_MAC_EXT | FLOW_RSS);
+}
+
 static int mlx5i_set_rxnfc(struct net_device *dev, struct ethtool_rxnfc *cmd)
 {
 	struct mlx5e_priv *priv = mlx5i_epriv(dev);