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: Cosmin-Florin Aluchenesei <aluchenesei.cosmin-florin@nxp.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/drivers/net/phy/aquantia.c b/drivers/net/phy/aquantia.c
index 9061afa..d3d35a7 100644
--- a/drivers/net/phy/aquantia.c
+++ b/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_startup(struct phy_device *phydev)
 {
-	u32 reg, speed;
+	u32 speed;
 	int i = 0;
+	int reg;
 
 	phydev->duplex = DUPLEX_FULL;