M451 CAN API support mask feature

Author: cyliangtw

targets/TARGET_NUVOTON/TARGET_M451/can_api.c

@@ -285,7 +285,17 @@ int can_mode(can_t *obj, CanMode mode)
 
 int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle)
 {
-    return CAN_SetRxMsg((CAN_T *)NU_MODBASE(obj->can), handle , (uint32_t)format, id);
+    uint32_t numask = mask;
+    if( numask == 0x0000 )
+    {
+      return CAN_SetRxMsg((CAN_T *)NU_MODBASE(obj->can), handle, (uint32_t)format, id);
+    }
+    if( format == CANStandard )
+    {
+      numask = (mask << 18);
+    }
+    numask = (numask | CAN_IF_MASK2_MDIR_Msk | CAN_IF_MASK2_MXTD_Msk);
+    return CAN_SetRxMsgAndMsk((CAN_T *)NU_MODBASE(obj->can), handle, (uint32_t)format, id, numask);
 }