net: stmmac: drop the ethtool begin() callback

This callback doesn't seem to serve much purpose, and prevents things
like:

    - systemd.link files from disabling autonegotiation
    - carrier detection in NetworkManager
    - any ethtool setting

prior to userspace bringing the link up.

The only fear I can think of is accessing unclocked resources due to
pm_runtime, but ethtool ioctls handle that as of commit
f32a213 ("ethtool: runtime-resume netdev parent before ethtool ioctl ops")

Reviewed-by: Dmitry Dolenko <d.dolenko@metrotek.ru>
Tested-by: Dmitry Dolenko <d.dolenko@metrotek.ru>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c

@@ -438,13 +438,6 @@ static void stmmac_ethtool_setmsglevel(struct net_device *dev, u32 level)
 
 }
 
-static int stmmac_check_if_running(struct net_device *dev)
-{
-	if (!netif_running(dev))
-		return -EBUSY;
-	return 0;
-}
-
 static int stmmac_ethtool_get_regs_len(struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
@@ -1273,7 +1266,6 @@ static int stmmac_set_tunable(struct net_device *dev,
 static const struct ethtool_ops stmmac_ethtool_ops = {
 	.supported_coalesce_params = ETHTOOL_COALESCE_USECS |
 				     ETHTOOL_COALESCE_MAX_FRAMES,
-	.begin = stmmac_check_if_running,
 	.get_drvinfo = stmmac_ethtool_getdrvinfo,
 	.get_msglevel = stmmac_ethtool_getmsglevel,
 	.set_msglevel = stmmac_ethtool_setmsglevel,