perf tests shell kprobes: Add missing description as used by 'perf test' output

Before:

  root@x1:~# perf test 76
   76: SPDX-License-Identifier: GPL-2.0                                : Ok
  root@x1:~#

After:

  root@x1:~# perf test 76
   76: Add 'perf probe's, list and remove them.                        : Ok
  root@x1:~#
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Veronika Molnarova <vmolnaro@redhat.com>
Link: https://lore.kernel.org/lkml/ZigRDKUGkcDqD-yW@x1Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/base_probe/test_adding_kernel.sh

 #!/bin/bash
+# Add 'perf probe's, list and remove them
 # SPDX-License-Identifier: GPL-2.0
 
 #