STM32: F2: put can_s struct under DEVICE_CAN option

LMESTM · LMESTM · commit 5997811d4646 · 2017-09-05T10:27:21.000+02:00
In case of F2 devices without CAN support.
diff --git a/targets/TARGET_STM/TARGET_STM32F2/objects.h b/targets/TARGET_STM/TARGET_STM32F2/objects.h
@@ -136,11 +136,13 @@ struct pwmout_s {
     uint8_t inverted;
 };
 
+#ifdef DEVICE_CAN
 struct can_s {
     CAN_HandleTypeDef CanHandle;
     int index;
     int hz;
 };
+#endif
 
 #define GPIO_IP_WITHOUT_BRR
 #include "gpio_object.h"
