firmware_TouchMTB: fix descriptions in the summary report

Make summary report more descriptive.

Metrics statistics:           fw_11.27  description (lower is better)
---------------------------------------------------------------------
CountPacketsValidator
  pct of incorrect cases (%):      0.0  an incorrect case is one where a swipe
                                        has less than 3 packets reported
CountTrackingIDValidator
  pct of incorrect cases (%):     6.90  an incorrect case is one where there are
                                        an incorrect number of fingers detected

BUG=chromium:235753
TEST=Replay the logs on link. Observe that the descriptions
are shown like above:
$ cd /usr/local/autotest/tests/firmware_TouchMTB
$ tools/machine_replay.sh -b tests/logs/lumpy -s
$ ./summary.sh -d /tmp -m f

Change-Id: I6a0fcba8fe2b98f5bd3046e86f45843a2268b1d3
Reviewed-on: https://chromium-review.googlesource.com/66632
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Tested-by: Shyh-In Hwang <josephsih@chromium.org>
Commit-Queue: Shyh-In Hwang <josephsih@chromium.org>
2 files changed