perf probe: Use skip_spaces() for argv handling

The skip_sep() routine has the same implementation as skip_spaces(),
recently adopted from the kernel, sources, switch to it.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-0ix211a81z2016dl5nmtdci4@git.kernel.org


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