srcu: Make num_rcu_lvl[] array be external

This commit makes the num_rcu_lvl[] array external so that SRCU can
make use of it for initializing its upcoming srcu_node tree.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/rcu.h

@@ -195,6 +195,7 @@ extern void resched_cpu(int cpu);
 #include <linux/rcu_node_tree.h>
 
 extern int rcu_num_lvls;
+extern int num_rcu_lvl[];
 extern int rcu_num_nodes;
 static bool rcu_fanout_exact;
 static int rcu_fanout_leaf;

kernel/rcu/tree.c

@@ -123,7 +123,7 @@ static int rcu_fanout_leaf = RCU_FANOUT_LEAF;
 module_param(rcu_fanout_leaf, int, 0444);
 int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
 /* Number of rcu_nodes at specified level. */
-static int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
+int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
 int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
 /* panic() on RCU Stall sysctl. */
 int sysctl_panic_on_rcu_stall __read_mostly;