perf tools: Don't die on a print function

Trying to remove die() calls from library functions, postponing exiting
to the tool main code.

Link: http://lkml.kernel.org/n/tip-ackxq5nqe39gunln3tkczs42@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>