net: of_get_phy_mode: Change API to solve int/unit warnings

Before this change of_get_phy_mode() returned an enum,
phy_interface_t. On error, -ENODEV etc, is returned. If the result of
the function is stored in a variable of type phy_interface_t, and the
compiler has decided to represent this as an unsigned int, comparision
with -ENODEV etc, is a signed vs unsigned comparision.

Fix this problem by changing the API. Make the function return an
error, or 0 on success, and pass a pointer, of type phy_interface_t,
where the phy mode should be stored.

v2:
Return with *interface set to PHY_INTERFACE_MODE_NA on error.
Add error checks to all users of of_get_phy_mode()
Fixup a few reverse christmas tree errors
Fixup a few slightly malformed reverse christmas trees

v3:
Fix 0-day reported errors.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index 7ba35a0..e19b49c 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -3183,6 +3183,7 @@ static struct sh_eth_plat_data *sh_eth_parse_dt(struct device *dev)
 {
 	struct device_node *np = dev->of_node;
 	struct sh_eth_plat_data *pdata;
+	phy_interface_t interface;
 	const char *mac_addr;
 	int ret;
 
@@ -3190,10 +3191,10 @@ static struct sh_eth_plat_data *sh_eth_parse_dt(struct device *dev)
 	if (!pdata)
 		return NULL;
 
-	ret = of_get_phy_mode(np);
-	if (ret < 0)
+	ret = of_get_phy_mode(np, &interface);
+	if (ret)
 		return NULL;
-	pdata->phy_interface = ret;
+	pdata->phy_interface = interface;
 
 	mac_addr = of_get_mac_address(np);
 	if (!IS_ERR(mac_addr))