rcu-tasks: Add #include of rcupdate_trace.h to update.c

Although this is in some strict sense unnecessary, it is good to allow
the compiler to compare the function declaration with its definition.
This commit therefore adds a #include of linux/rcupdate_trace.h to
kernel/rcu/update.c.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/update.c

@@ -42,6 +42,7 @@
 #include <linux/kprobes.h>
 #include <linux/slab.h>
 #include <linux/irq_work.h>
+#include <linux/rcupdate_trace.h>
 
 #define CREATE_TRACE_POINTS