perf test: Add missing verbose output explaining the reason for failure

One of the branches leading to an error had no debug message emitted,
fix it, the new lines are:

  # perf test -v kallsyms
<SNIP>
  0xffffffff81001000: diff name v: xen_hypercall_set_trap_table k: hypercall_page
  0xffffffff810691f0: diff name v: try_to_free_pud_page k: try_to_free_pmd_page
<SNIP>
  0xffffffff8150bb20: diff name v: wakeup_expire_count_show.part.5 k: wakeup_active_count_show.part.7
  0xffffffff816bc7f0: diff name v: phys_switch_id_show.part.11 k: phys_port_name_show.part.12
  0xffffffff817bbb90: diff name v: __do_softirq k: __softirqentry_text_start
<SNIP>

This in turn exercises another bug, still under investigation, because those
aliases _are_ in kallsyms, with the same name...

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: ab414dcd ("perf test: Fixup aliases checking in the 'vmlinux matches kallsyms' test")
Link: http://lkml.kernel.org/n/tip-5fhea7a54a54gsmagu9obpr4@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/vmlinux-kallsyms.c

@@ -163,6 +163,9 @@ int test__vmlinux_matches_kallsyms(int subtest __maybe_unused)
 
 					pr_debug("%#" PRIx64 ": diff name v: %s k: %s\n",
 						 mem_start, sym->name, pair->name);
+				} else {
+					pr_debug("%#" PRIx64 ": diff name v: %s k: %s\n",
+						 mem_start, sym->name, first_pair->name);
 				}
 			}
 		} else