include/linux/relay.h: fix percpu annotation in struct rchan

The percpu member of this structure is declared as:
	struct ... ** __percpu member;
So its type is:
	__percpu pointer to pointer to struct ...

But looking at how it's used, its type should be:
	pointer to __percpu pointer to struct ...
and it should thus be declared as:
	struct ... * __percpu *member;

So fix the placement of '__percpu' in the definition of this
structures.

This silents a few Sparse's warnings like:
	warning: incorrect type in initializer (different address spaces)
	  expected void const [noderef] <asn:3> *__vpp_verify
	  got struct sched_domain **

Link: http://lkml.kernel.org/r/20190118144902.79065-1-luc.vanoostenryck@gmail.com
Fixes: 017c59c042 ("relay: Use per CPU constructs for the relay channel buffer pointers")
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Jens Axboe <axboe@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/relay.h

@@ -66,7 +66,7 @@ struct rchan
 	struct kref kref;		/* channel refcount */
 	void *private_data;		/* for user-defined data */
 	size_t last_toobig;		/* tried to log event > subbuf size */
-	struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */
+	struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
 	int is_global;			/* One global buffer ? */
 	struct list_head list;		/* for channel list */
 	struct dentry *parent;		/* parent dentry passed to open */