net: spacemit: Check netif_running() in emac_set_pauseparam()

Currently, emac_set_pauseparam() will oops if userspace calls it while
the interface is not up, because phydev is NULL, but it is still
accessed in emac_set_fc() and emac_set_fc_autoneg().

Check for netif_running(dev) in emac_set_pauseparam() before proceeding.

Fixes: bfec6d7f20 ("net: spacemit: Add K1 Ethernet MAC")
Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251103-k1-ethernet-remove-fc-v3-1-2083770cd282@iscas.ac.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/spacemit/k1_emac.c

@@ -1441,6 +1441,9 @@ static int emac_set_pauseparam(struct net_device *dev,
 	struct emac_priv *priv = netdev_priv(dev);
 	u8 fc = 0;
 
+	if (!netif_running(dev))
+		return -ENETDOWN;
+
 	priv->flow_control_autoneg = pause->autoneg;
 
 	if (pause->autoneg) {