io_uring: extract io_uring_files_cancel() in io_uring_task_cancel()

Extract io_uring_files_cancel() call in io_uring_task_cancel() to make
io_uring_files_cancel() and io_uring_task_cancel() coherent and easy to
read.
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/io_uring.h

@@ -17,7 +17,8 @@ static inline void io_uring_files_cancel(struct files_struct *files)
 }
 static inline void io_uring_task_cancel(void)
 {
-	return io_uring_files_cancel(NULL);
+	if (current->io_uring)
+		__io_uring_cancel(NULL);
 }
 static inline void io_uring_free(struct task_struct *tsk)
 {