defines: prevent redefinition of UNUSED

To prevent compiler warnings/errors we have to wrap the definition of
UNUSED with an ifndef. So there are no problems if this is already
defined in the project

Signed-off-by: Peter Tönz <peter.tonz@husqvarnagroup.com>

Drivers/STM32F4xx_HAL_Driver/Inc/stm32f4xx_hal_def.h

@@ -54,7 +54,9 @@ typedef enum
 
 /* Exported macro ------------------------------------------------------------*/
 
-#define UNUSED(X) (void)X      /* To avoid gcc/g++ warnings */
+#ifndef UNUSED
+  #define UNUSED(X) (void)X      /* To avoid gcc/g++ warnings */
+#endif
 
 #define HAL_MAX_DELAY      0xFFFFFFFFU