net: phy: vitesse: Fix incorrect test for timeout

In vsc8514_config there is a while loop for detecting a config failure
using a timeout counter with a post-decrement. In the case of a timeout
this will result in the loop exiting with timeout == -1 so use that as
the test below the loop to detect that the timeout occurred.

This issue was found by Smatch.

Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>

drivers/net/phy/vitesse.c

@@ -239,7 +239,7 @@ static int vsc8514_config(struct phy_device *phydev)
 	while ((val & MIIM_VSC8514_18G_CMDSTAT) && timeout--)
 		val = phy_read(phydev, MDIO_DEVAD_NONE, MIIM_VSC8514_GENERAL18);
 
-	if (0 == timeout) {
+	if (timeout == -1) {
 		printf("PHY 8514 config failed\n");
 		return -1;
 	}