FS-Cache: Replace zero-length array with flexible-array

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://github.com/KSPP/linux/issues/21Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

include/linux/fscache-cache.h

@@ -46,7 +46,7 @@ struct fscache_cache_tag {
 	unsigned long		flags;
 #define FSCACHE_TAG_RESERVED	0		/* T if tag is reserved for a cache */
 	atomic_t		usage;
-	char			name[0];	/* tag name */
+	char			name[];	/* tag name */
 };
 
 /*