sched/cputime: Refactor the cputime_adjust() code

Address a Coverity false positive, which is caused by overly
convoluted code:

Value assigned to variable 'utime' at line 619:utime = rtime;
is overwritten at line 642:utime = rtime - stime; before it
can be used. This makes such variable assignment useless.

Remove this variable assignment and refactor the code related.

Addresses-Coverity-ID: 1371643
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Cc: Frans Klaver <fransklaver@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/20170629184128.GA5271@embeddedgusSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/cputime.c

@@ -615,19 +615,13 @@ static void cputime_adjust(struct task_cputime *curr,
 	 * userspace. Once a task gets some ticks, the monotonicy code at
 	 * 'update' will ensure things converge to the observed ratio.
 	 */
-	if (stime == 0) {
-		utime = rtime;
-		goto update;
-	}
-
-	if (utime == 0) {
+	if (stime != 0) {
+		if (utime == 0)
 			stime = rtime;
-		goto update;
-	}
-
+		else
 			stime = scale_stime(stime, rtime, stime + utime);
+	}
 
-update:
 	/*
 	 * Make sure stime doesn't go backwards; this preserves monotonicity
 	 * for utime because rtime is monotonic.