fs: 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/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

include/linux/fs.h

@@ -3285,7 +3285,7 @@ static inline ino_t parent_ino(struct dentry *dentry)
  */
 struct simple_transaction_argresp {
 	ssize_t size;
-	char data[0];
+	char data[];
 };
 
 #define SIMPLE_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct simple_transaction_argresp))