generic: b53: fix reverted error check in probe

b53_switch_detect returns value returned by b53_read8, which is 0 for
success. So fail (and return error) only if b53_switch_detect returned
something else than 0. This fixes supported and advertising being zeros
for MDIO access.

Cc: Jonas Gorski <jogo@openwrt.org>
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 35534

target/linux/generic/files/drivers/net/phy/b53/b53_mdio.c

@@ -267,7 +267,7 @@ static int b53_phy_probe(struct phy_device *phydev)
 	mutex_init(&dev.reg_mutex);
 
 	ret = b53_switch_detect(&dev);
-	if (!ret)
+	if (ret)
 		return ret;
 
 	if (is5325(&dev) || is5365(&dev))