perf script: Use fprintf like printing uniformly

We've been mixing print() with fprintf() style printing for a while, but
now we need to use fprintf() like syntax uniformly as a preparatory
patch for supporting printing to different files, one per event.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: yuzhoujian <yuzhoujian@didichuxing.com>
Link: http://lkml.kernel.org/n/tip-kv5z3v8ptfghbarv3a9usvin@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>