drivers: net: aquantia: fix unsigned compared against 0

Change the reg variable to not be unsigned so that we not get into an
unsigned compared against 0.
Signed-off-by: NCosmin-Florin Aluchenesei <aluchenesei.cosmin-florin@nxp.com>
Reviewed-by: NRamon Fried <rfried.dev@gmail.com>

drivers/net/phy/aquantia.c

@@ -3,7 +3,7 @@
  * Aquantia PHY drivers
  *
  * Copyright 2014 Freescale Semiconductor, Inc.
- * Copyright 2018 NXP
+ * Copyright 2018, 2021 NXP
  */
 #include <config.h>
 #include <common.h>
@@ -554,8 +554,9 @@ int aquantia_config(struct phy_device *phydev)
 
 int aquantia_startup(struct phy_device *phydev)
 {
-	u32 reg, speed;
+	u32 speed;
 	int i = 0;
+	int reg;
 
 	phydev->duplex = DUPLEX_FULL;