[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/fork.c b/kernel/fork.c
index da4a6a1..b058c58 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1023,8 +1023,8 @@
  */
 static void posix_cpu_timers_init(struct task_struct *tsk)
 {
-	tsk->cputime_expires.prof_exp = cputime_zero;
-	tsk->cputime_expires.virt_exp = cputime_zero;
+	tsk->cputime_expires.prof_exp = 0;
+	tsk->cputime_expires.virt_exp = 0;
 	tsk->cputime_expires.sched_exp = 0;
 	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
@@ -1132,14 +1132,10 @@
 
 	init_sigpending(&p->pending);
 
-	p->utime = cputime_zero;
-	p->stime = cputime_zero;
-	p->gtime = cputime_zero;
-	p->utimescaled = cputime_zero;
-	p->stimescaled = cputime_zero;
+	p->utime = p->stime = p->gtime = 0;
+	p->utimescaled = p->stimescaled = 0;
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
-	p->prev_utime = cputime_zero;
-	p->prev_stime = cputime_zero;
+	p->prev_utime = p->prev_stime = 0;
 #endif
 #if defined(SPLIT_RSS_COUNTING)
 	memset(&p->rss_stat, 0, sizeof(p->rss_stat));