sched/cputime: Add dummy cputime_adjust() implementation for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

cfb766da ("sched/cputime: Expose cputime_adjust()") made
cputime_adjust() public for cgroup basic cpu stat support; however,
the commit forgot to add a dummy implementaiton for
CONFIG_VIRT_CPU_ACCOUNTING_NATIVE leading to compiler errors on some
s390 configurations.

Fix it by adding the missing dummy implementation.
Reported-by: “kbuild-all@01.org” <kbuild-all@01.org>
Fixes: cfb766da ("sched/cputime: Expose cputime_adjust()")
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/sched/cputime.c

@@ -447,6 +447,13 @@ void vtime_account_irq_enter(struct task_struct *tsk)
 EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
 #endif /* __ARCH_HAS_VTIME_ACCOUNT */
 
+void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
+		    u64 *ut, u64 *st)
+{
+	*ut = curr->utime;
+	*st = curr->stime;
+}
+
 void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
 {
 	*ut = p->utime;