perf script: Remove workqueue-stats script

The tracepoints used by the workqueue-stats script no longer exist so
trying to run the script results in:

  # perf script record workqueue-stats
  invalid or unsupported event: 'workqueue:workqueue_creation'
  Run 'perf list' for a list of valid events

So remove the script until it can be reworked using the new workqueue
tracepoints.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Link: http://lkml.kernel.org/r/e7a7637d5df9df86887c3bff7683574665ec5360.1358527965.git.tom.zanussi@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>