Docs/RCU/rculist_nulls: Fix trivial coding style

Lookup example of non-hlist_nulls management is missing a semicolon, and
having inconsistent indentation (one line is using single space
indentation while others are using two spaces indentation).  Fix the
trivial issues.
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Documentation/RCU/rculist_nulls.rst

@@ -26,7 +26,7 @@ algorithms:
 ::
 
   begin:
-  rcu_read_lock()
+  rcu_read_lock();
   obj = lockless_lookup(key);
   if (obj) {
     if (!try_get_ref(obj)) { // might fail for free objects
@@ -70,8 +70,8 @@ And note the traditional hlist_for_each_entry_rcu() misses this smp_rmb()::
        pos && ({ prefetch(pos->next); 1; }) &&
        ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; });
        pos = rcu_dereference(pos->next))
-   if (obj->key == key)
-     return obj;
+    if (obj->key == key)
+      return obj;
   return NULL;
 
 Quoting Corey Minyard::