Add CAN object structure

Author: bcostm

targets/TARGET_STM/TARGET_STM32F4/TARGET_NUCLEO_F412ZG/objects.h

@@ -46,6 +46,11 @@ struct analogin_s {
     uint8_t channel;
 };
 
+struct can_s {
+    CANName can;
+    int index;
+};
+
 struct trng_s {
     RNG_HandleTypeDef handle;
 };