Reactivate all the cores in cpu.sh.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/1004763002

Cr-Commit-Position: refs/heads/master@{#27170}

tools/cpu.sh

@@ -31,7 +31,7 @@ single_core() {
 
 all_cores() {
   echo "Reactivating all CPU cores"
-  for (( i=2; i<=$MAXID; i++ )); do
+  for (( i=1; i<=$MAXID; i++ )); do
     echo 1 > $CPUPATH/cpu$i/online
   done
 }