perf tests: Remove bash constructs from stat_all_pmu.sh

The tests were passing but without testing and were printing the
following:

  $ ./perf test -v 90
  90: perf all PMU test                                               :
  --- start ---
  test child forked, pid 51650
  Testing cpu/branch-instructions/
  ./tests/shell/stat_all_pmu.sh: 10: [:
   Performance counter stats for 'true':

             137,307      cpu/branch-instructions/

         0.001686672 seconds time elapsed

         0.001376000 seconds user
         0.000000000 seconds sys: unexpected operator

Changing the regexes to a grep works in sh and prints this:

  $ ./perf test -v 90
  90: perf all PMU test                                               :
  --- start ---
  test child forked, pid 60186
  [...]
  Testing tlb_flush.stlb_any
  test child finished with 0
  ---- end ----
  perf all PMU test: Ok
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20211028134828.65774-4-james.clark@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/stat_all_pmu.sh

@@ -7,11 +7,11 @@ set -e
 for p in $(perf list --raw-dump pmu); do
   echo "Testing $p"
   result=$(perf stat -e "$p" true 2>&1)
-  if [[ ! "$result" =~ "$p" ]] && [[ ! "$result" =~ "<not supported>" ]]; then
+  if ! echo "$result" | grep -q "$p" && ! echo "$result" | grep -q "<not supported>" ; then
     # We failed to see the event and it is supported. Possibly the workload was
     # too small so retry with something longer.
     result=$(perf stat -e "$p" perf bench internals synthesize 2>&1)
-    if [[ ! "$result" =~ "$p" ]]; then
+    if ! echo "$result" | grep -q "$p" ; then
       echo "Event '$p' not printed in:"
       echo "$result"
       exit 1