perf sched: Use linux/time64.h

Probably the next step is to introduce linux/time.h and use
timespec_to_ns(), etc.

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: Steven Rostedt <rostedt@goodmis.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-4nqhskn27fn93cz3ukbc8drf@git.kernel.org


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