perf tools: Remove some needless die() calls from the main routine

Some would just call exit() anyway right after calling die() and the
main routine doesn't have to call it, just return the exit value.

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-nzq0sdur6oq6lgkt2ipf4o8s@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>