[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/fs/proc/array.c b/fs/proc/array.c
index 3a1dafd..8c344f0 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -394,8 +394,8 @@
 
 	sigemptyset(&sigign);
 	sigemptyset(&sigcatch);
-	cutime = cstime = utime = stime = cputime_zero;
-	cgtime = gtime = cputime_zero;
+	cutime = cstime = utime = stime = 0;
+	cgtime = gtime = 0;
 
 	if (lock_task_sighand(task, &flags)) {
 		struct signal_struct *sig = task->signal;
@@ -423,14 +423,14 @@
 			do {
 				min_flt += t->min_flt;
 				maj_flt += t->maj_flt;
-				gtime = cputime_add(gtime, t->gtime);
+				gtime += t->gtime;
 				t = next_thread(t);
 			} while (t != task);
 
 			min_flt += sig->min_flt;
 			maj_flt += sig->maj_flt;
 			thread_group_times(task, &utime, &stime);
-			gtime = cputime_add(gtime, sig->gtime);
+			gtime += sig->gtime;
 		}
 
 		sid = task_session_nr_ns(task, ns);