perf report: Check argument before calling setup_browser()

This is necessary to get rid of the browser dependency from
usage_with_options() and its friends.  Because there's no code
changing the argc and argv, it'd be ok to check it early.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1449716459-23004-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>