net: davinci_emac: 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: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/davinci_emac.c

@@ -481,6 +481,7 @@ static int emac_set_coalesce(struct net_device *ndev,
  * Ethtool support for EMAC adapter
  */
 static const struct ethtool_ops ethtool_ops = {
+	.supported_coalesce_params = ETHTOOL_COALESCE_RX_USECS,
 	.get_drvinfo = emac_get_drvinfo,
 	.get_link = ethtool_op_get_link,
 	.get_coalesce = emac_get_coalesce,