The callers of this function (perf_event__process_tracing_data) already
handles a negative value return as error, so just use pr_err() to log
the problem and return -1 instead of panic'ing.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-eeeljnecpi0zi5s7ux1mzdv9@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>