fix:stm32 can build error (#10909)

Author: CYFS3

bsp/stm32/libraries/HAL_Drivers/drivers/drv_can.c

@@ -500,7 +500,7 @@ static rt_err_t _can_control(struct rt_can_device *can, int cmd, void *arg)
  *
  * @return `RT_EOK` on success, or an error code on failure.
  */
-static int _can_sendmsg(struct rt_can_device *can, const void *buf, rt_uint32_t box_num)
+static rt_ssize_t _can_sendmsg(struct rt_can_device *can, const void *buf, rt_uint32_t box_num)
 {
     CAN_HandleTypeDef *hcan;
     hcan = &((struct stm32_can *) can->parent.user_data)->CanHandle;
@@ -649,7 +649,7 @@ static rt_ssize_t _can_sendmsg_nonblocking(struct rt_can_device *can, const void
     return RT_EOK;
 }
 
-static int _can_recvmsg(struct rt_can_device *can, void *buf, rt_uint32_t fifo)
+static rt_ssize_t _can_recvmsg(struct rt_can_device *can, void *buf, rt_uint32_t fifo)
 {
     HAL_StatusTypeDef status;
     CAN_HandleTypeDef *hcan;