perf script: Use pr_debug where appropriate

perf script: Use pr_debug where appropriate

We have facilities for reporting unexpected, unlikely errors, use them.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: yuzhoujian <yuzhoujian@didichuxing.com>
Link: http://lkml.kernel.org/n/tip-c7j22xfjf1j773g7ufp607q0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>