net: broadcom/bcmsysport: Fix signedness in bcm_sysport_probe()

[ Upstream commit 25a584955f020d6ec499c513923fb220f3112d2b ]

The "priv->phy_interface" variable is an enum and in this context GCC
will treat it as unsigned so the error handling will never be
triggered.

Fixes: 80105bef ("net: systemport: add Broadcom SYSTEMPORT Ethernet MAC driver")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/ethernet/broadcom/bcmsysport.c

@@ -2470,7 +2470,7 @@ static int bcm_sysport_probe(struct platform_device *pdev)
 
 	priv->phy_interface = of_get_phy_mode(dn);
 	/* Default to GMII interface mode */
-	if (priv->phy_interface < 0)
+	if ((int)priv->phy_interface < 0)
 		priv->phy_interface = PHY_INTERFACE_MODE_GMII;
 
 	/* In the case of a fixed PHY, the DT node associated