perf/trace/scripting: failed-syscalls script cleanup

A couple small fixes for the failed syscalls script:

- The script description says it can be restricted to a specific comm,
  make it so.

- silence the match output in the shell script

Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <1273466820-9330-2-git-send-email-tzanussi@gmail.com>
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/perl/bin/failed-syscalls-report

@@ -2,7 +2,7 @@
 # description: system-wide failed syscalls
 # args: [comm]
 if [ $# -gt 0 ] ; then
-    if ! expr match "$1" "-" ; then
+    if ! expr match "$1" "-" > /dev/null ; then
 	comm=$1
 	shift
     fi