perf tools: Remove redundant err variable

Return value from perf_event__process_tracing_data() directly instead
of taking this in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20220112080109.666800-1-chi.minghao@zte.com.cn


Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>