idr: fix RCU lockdep splat in idr_get_next()

Convert to rcu_dereference_raw() given that many callers may have many
different locking models.
Located-by: Miles Lane <miles.lane@gmail.com>
Tested-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

lib/idr.c

@@ -602,7 +602,7 @@ void *idr_get_next(struct idr *idp, int *nextidp)
 	/* find first ent */
 	n = idp->layers * IDR_BITS;
 	max = 1 << n;
-	p = rcu_dereference(idp->top);
+	p = rcu_dereference_raw(idp->top);
 	if (!p)
 		return NULL;
 
@@ -610,7 +610,7 @@ void *idr_get_next(struct idr *idp, int *nextidp)
 		while (n > 0 && p) {
 			n -= IDR_BITS;
 			*paa++ = p;
-			p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
+			p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
 		}
 
 		if (p) {