[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/uptime.c b/fs/proc/uptime.c
index 766b1d4..ac52436 100644
--- a/fs/proc/uptime.c
+++ b/fs/proc/uptime.c
@@ -12,10 +12,10 @@
 	struct timespec uptime;
 	struct timespec idle;
 	int i;
-	cputime_t idletime = cputime_zero;
+	cputime_t idletime = 0;
 
 	for_each_possible_cpu(i)
-		idletime = cputime64_add(idletime, kstat_cpu(i).cpustat.idle);
+		idletime += kstat_cpu(i).cpustat.idle;
 
 	do_posix_clock_monotonic_gettime(&uptime);
 	monotonic_to_bootbased(&uptime);