Toolchain-utils: replace xrange with range on results_cache.py

xrange builtint is replaced by range on Python3. Use range instead of xrange on
results_cache.py.

BUG=chromium:986617

TEST=local tests

Change-Id: I729b12a92b75dbd355fad3012205765a648be538
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1717449
Tested-by: Jian Cai <jiancai@google.com>
Reviewed-by: George Burgess <gbiv@chromium.org>
diff --git a/crosperf/results_cache.py b/crosperf/results_cache.py
index ab16e98..6124dbe 100644
--- a/crosperf/results_cache.py
+++ b/crosperf/results_cache.py
@@ -655,7 +655,7 @@
       fields = line.split(',')
       if len(fields) != len(labels):
         continue
-      for i in xrange(1, len(labels)):
+      for i in range(1, len(labels)):
         key = '%s %s' % (fields[0], labels[i])
         value = fields[i]
         self.keyvals[key] = value