freevxfs: Replace one-element array with flexible array member

Replace the deprecated one-element array with a modern flexible array
member in the struct vxfs_dirblk.

Link: KSPP#79
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://lore.kernel.org/r/20241103121707.102838-3-thorsten.blum@linux.dev
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/freevxfs/vxfs_dir.h

@@ -25,7 +25,7 @@
 struct vxfs_dirblk {
 	__fs16		d_free;		/* free space in dirblock */
 	__fs16		d_nhash;	/* no of hash chains */
-	__fs16		d_hash[1];	/* hash chain */
+	__fs16		d_hash[];	/* hash chain */
 };
 
 /*