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: https://github.com/KSPP/linux/issues/79
Signed-off-by: Thorsten Blum <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>

fs/freevxfs/vxfs_dir.h

···
 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 */
 };
 
 /*