net: phy: bcm54140: fix less than zero comparison on an unsigned

Currently the unsigned variable tmp is being checked for an negative
error return from the call to bcm_phy_read_rdb and this can never
be true since tmp is unsigned.  Fix this by making tmp a plain int.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: 4406d36d ("net: phy: bcm54140: add hwmon support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Michael Walle <michael@walle.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/bcm54140.c

@@ -191,7 +191,8 @@ static int bcm54140_hwmon_read_alarm(struct device *dev, unsigned int bit,
 static int bcm54140_hwmon_read_temp(struct device *dev, u32 attr, long *val)
 {
 	struct phy_device *phydev = dev_get_drvdata(dev);
-	u16 reg, tmp;
+	u16 reg;
+	int tmp;
 
 	switch (attr) {
 	case hwmon_temp_input:
@@ -224,7 +225,8 @@ static int bcm54140_hwmon_read_in(struct device *dev, u32 attr,
 				  int channel, long *val)
 {
 	struct phy_device *phydev = dev_get_drvdata(dev);
-	u16 bit, reg, tmp;
+	u16 bit, reg;
+	int tmp;
 
 	switch (attr) {
 	case hwmon_in_input: