perf test: Restrict uniquifying test to machines with 'uncore_imc'

The test would fail if target machine does not have 'uncore_imc'
devices.

Since event uniquifying behavior is similar among different
architectures, we are restricting the test to only run on machines with
`uncore_imc` devices.

Suggested-by: Ian Rogers <[e-mail]>
Signed-off-by: Chun-Tse Shao <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
[ Skip the test, i.e. return 2, instead of returning 0 as if the test had succeed ]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/stat+event_uniquifying.sh

···
 err=0
 
 test_event_uniquifying() {
-  # We use `clockticks` to verify the uniquify behavior.
+  # We use `clockticks` in `uncore_imc` to verify the uniquify behavior.
+  pmu="uncore_imc"
   event="clockticks"
 
   # If the `-A` option is added, the event should be uniquified.
···
   echo "stat event uniquifying test"
   uniquified_event_array=()
 
+  # Skip if the machine does not have `uncore_imc` device.
+  if ! ${perf_tool} list pmu | grep -q ${pmu}; then
+    echo "Target does not support PMU ${pmu} [Skipped]"
+    err=2
+    return
+  fi
+
   # Check how many uniquified events.
   while IFS= read -r line; do
     uniquified_event=$(echo "$line" | awk '{print $1}')
     uniquified_event_array+=("${uniquified_event}")
-  done < <(${perf_tool} list -v ${event} | grep "\[Kernel PMU event\]")
+  done < <(${perf_tool} list -v ${event} | grep ${pmu})
 
   perf_command="${perf_tool} stat -e $event -A -o ${stat_output} -- true"
   $perf_command