io_uring: replace zero-length array with flexible-array member

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/78
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/uapi/linux/io_uring.h

@@ -495,7 +495,7 @@ struct io_uring_probe {
 	__u8 ops_len;	/* length of ops[] array below */
 	__u16 resv;
 	__u32 resv2[3];
-	struct io_uring_probe_op ops[0];
+	struct io_uring_probe_op ops[];
 };
 
 struct io_uring_restriction {