tools headers UAPI: Sync sched.h with the kernel

To get the changes in:

  ef2c41cf ("clone3: allow spawning processes into cgroups")

Add that to 'perf trace's clone 'flags' decoder.

This silences this perf build warning:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/sched.h' differs from latest version at 'include/uapi/linux/sched.h'
  diff -u tools/include/uapi/linux/sched.h include/uapi/linux/sched.h

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>