sched/core: Fix CONFIG_GCC_PLUGIN_RANDSTRUCT build fail

As a temporary build fix, the proper cleanup needs more work.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Eric Biggers <ebiggers@kernel.org>
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Suggested-by: Kees Cook <keescook@chromium.org>
Fixes: a1488664 ("sched: Replace rq::wake_list")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -654,8 +654,10 @@ struct task_struct {
 	unsigned int			ptrace;
 
 #ifdef CONFIG_SMP
+	struct {
 		struct llist_node		wake_entry;
 		unsigned int			wake_entry_type;
+	};
 	int				on_cpu;
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 	/* Current CPU: */