[S390] cputime: add sparse checking and cleanup

Make cputime_t and cputime64_t nocast to enable sparse checking to
detect incorrect use of cputime. Drop the cputime macros for simple
scalar operations. The conversion macros are still needed.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 563f136..3f8ee8a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -178,8 +178,7 @@
 	write_lock_irq(&tasklist_lock);
 	for_each_process(p) {
 		if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
-		    (!cputime_eq(p->utime, cputime_zero) ||
-		     !cputime_eq(p->stime, cputime_zero)))
+		    (p->utime || p->stime))
 			printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
 				"(state = %ld, flags = %x)\n",
 				p->comm, task_pid_nr(p), cpu,