net: mdio: Fix ENOMEM return value in BCM6368 mux bus controller

Error values inside the probe function must be < 0. The ENOMEM return
value has the wrong sign: it is positive instead of negative.
Add a minus sign.

Fixes: e2397567 ("net: mdio: Add BCM6368 MDIO mux bus controller")
Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220428211931.8130-1-dossche.niels@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/mdio/mdio-mux-bcm6368.c

@@ -115,7 +115,7 @@ static int bcm6368_mdiomux_probe(struct platform_device *pdev)
 	md->mii_bus = devm_mdiobus_alloc(&pdev->dev);
 	if (!md->mii_bus) {
 		dev_err(&pdev->dev, "mdiomux bus alloc failed\n");
-		return ENOMEM;
+		return -ENOMEM;
 	}
 
 	bus = md->mii_bus;