[tools] Fix type in GC eval script

tools/eval_gc_time.sh

 #!/bin/bash
 #
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Convenience Script used to rank GC NVP output.
 
 print_usage_and_die() {
   echo "Usage: $0 [OPTIONS]"
@@ skipping 44 matching lines @@
     -t|--top-level)
       TOP_LEVEL=yes
       ;;
     -c|--csv)
       CSV=" --csv "
       ;;
     -f|--file)
       LOGFILE=$2
       shift
       ;;
-    -f|--percentiles)
+    -p|--percentiles)
       PERCENTILES="--percentiles=$2"
       shift
       ;;
     *)
       break
       ;;
   esac
   shift
 done
 
@@ skipping 83 matching lines @@
       | $BASE_DIR/eval_gc_nvp.py \
       --no-histogram \
       --rank $RANK_MODE \
       $CSV \
       $PERCENTILES \
       ${INTERESTING_OLD_GEN_KEYS}
     ;;
   *)
     ;;
 esac