[BSP] fix compiling issue under gcc for STM32L4xx_HAL Library

bsp/stm32l475-iot-disco/Libraries/STM32L4xx_HAL_Driver/Inc/stm32l4xx_hal_def.h

@@ -48,6 +48,7 @@
 #include "stm32l4xx.h"
 #include "Legacy/stm32_hal_legacy.h"  /* Aliases file for old names compatibility */
 #include <stdio.h>
+#include <stdlib.h>
 
 /* Exported types ------------------------------------------------------------*/
 

bsp/stm32l476-nucleo/Libraries/STM32L4xx_HAL_Driver/Inc/stm32l4xx_hal_def.h

@@ -48,6 +48,7 @@
 #include "stm32l4xx.h"
 #include "Legacy/stm32_hal_legacy.h"  /* Aliases file for old names compatibility */
 #include <stdio.h>
+#include <stdlib.h>
 
 /* Exported types ------------------------------------------------------------*/