perf probe: Cleanup synthesize_probe_trace_command()

Cleanup synthesize_probe_trace_command() to simplify the code path.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/162282411361.452340.16886399333622147122.stgit@devnote2


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