perf test: Update sample filtering test

Now it can run the BPF filtering test with normal user if the BPF
objects are pinned by 'sudo perf record --setup-filter pin'. Let's
update the test case to verify the behavior. It'll skip the test if the
filter check is failed from a normal user, but it shows a message how to
set up the filters.

First, run the test as a normal user and it fails.

$ perf test -vv filtering
95: perf record sample filtering (by BPF) tests:
--- start ---
test child forked, pid 425677
Checking BPF-filter privilege
try 'sudo perf record --setup-filter pin' first. <<<--- here
bpf-filter test [Skipped permission]
---- end(-2) ----
95: perf record sample filtering (by BPF) tests : Skip

According to the message, run the perf record command to pin the BPF
objects.

$ sudo perf record --setup-filter pin

And re-run the test as a normal user.

$ perf test -vv filtering
95: perf record sample filtering (by BPF) tests:
--- start ---
test child forked, pid 424486
Checking BPF-filter privilege
Basic bpf-filter test
Basic bpf-filter test [Success]
Failing bpf-filter test
Error: task-clock event does not have PERF_SAMPLE_CPU
Failing bpf-filter test [Success]
Group bpf-filter test
Error: task-clock event does not have PERF_SAMPLE_CPU
Error: task-clock event does not have PERF_SAMPLE_CODE_PAGE_SIZE
Group bpf-filter test [Success]
---- end(0) ----
95: perf record sample filtering (by BPF) tests : Ok

Signed-off-by: Namhyung Kim <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: KP Singh <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Song Liu <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/record_bpf_filter.sh

···
 test_bpf_filter_priv() {
   echo "Checking BPF-filter privilege"
 
-  if [ "$(id -u)" != 0 ]
-  then
-    echo "bpf-filter test [Skipped permission]"
-    err=2
-    return
-  fi
   if ! perf record -e task-clock --filter 'period > 1' \
 	  -o /dev/null --quiet true 2>&1
   then
+    if [ "$(id -u)" != 0 ]
+    then
+      echo "try 'sudo perf record --setup-filter pin' first."
+      echo "bpf-filter test [Skipped permission]"
+      err=2
+      return
+    fi
     echo "bpf-filter test [Skipped missing BPF support]"
     err=2
     return