net: sxgbe: reject unsupported coalescing params

Set ethtool_ops->supported_coalesce_params to let
the core reject unsupported coalescing parameters.

This driver did not previously reject unsupported parameters.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/samsung/sxgbe/sxgbe_ethtool.c

@@ -476,6 +476,7 @@ static int sxgbe_get_regs_len(struct net_device *dev)
 }
 
 static const struct ethtool_ops sxgbe_ethtool_ops = {
+	.supported_coalesce_params = ETHTOOL_COALESCE_RX_USECS,
 	.get_drvinfo = sxgbe_getdrvinfo,
 	.get_msglevel = sxgbe_getmsglevel,
 	.set_msglevel = sxgbe_setmsglevel,