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

kernel/tracepoint.c

@@ -50,7 +50,7 @@ static bool ok_to_free_tracepoints;
  */
 struct tp_probes {
 	struct rcu_head rcu;
-	struct tracepoint_func probes[0];
+	struct tracepoint_func probes[];
 };
 
 static inline void *allocate_probes(int count)