rcu: Rename n_nocb_gp_requests to need_future_gp

CPUs going idle need to be able to indicate their need for future grace
periods.  A mechanism for doing this already exists for no-callbacks
CPUs, so the idea is to re-use that mechanism.  This commit therefore
moves the ->n_nocb_gp_requests field of the rcu_node structure out from
under the CONFIG_RCU_NOCB_CPU #ifdef and renames it to ->need_future_gp.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 96a27f9..034b524 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -194,9 +194,9 @@
 #ifdef CONFIG_RCU_NOCB_CPU
 	wait_queue_head_t nocb_gp_wq[2];
 				/* Place for rcu_nocb_kthread() to wait GP. */
-	int n_nocb_gp_requests[2];
-				/* Counts of upcoming no-CB GP requests. */
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
+	int need_future_gp[2];
+				/* Counts of upcoming no-CB GP requests. */
 	raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
 } ____cacheline_internodealigned_in_smp;