[stm32/libraries/HAL_Drivers/drv_eth.c]fixed read phy SR register return value conflicts with function's parameter

bsp/stm32/libraries/HAL_Drivers/drv_eth.c

@@ -411,11 +411,11 @@ static void phy_linkchange()
 
     if (status & (PHY_AUTONEGO_COMPLETE_MASK | PHY_LINKED_STATUS_MASK))
     {
-        rt_uint32_t SR;
+        rt_uint32_t SR = 0;
 
         phy_speed_new |= PHY_LINK;
 
-        SR = HAL_ETH_ReadPHYRegister(&EthHandle, PHY_Status_REG, (uint32_t *)&SR);
+        HAL_ETH_ReadPHYRegister(&EthHandle, PHY_Status_REG, (uint32_t *)&SR);
         LOG_D("phy control status reg is 0x%X", SR);
 
         if (PHY_Status_SPEED_100M(SR))