tools/sched_ext: fix getopt not re-parsed on restart

tools/sched_ext: fix getopt not re-parsed on restart

After goto restart, optind retains its advanced position from the
previous getopt loop, causing getopt() to immediately return -1.
This silently drops all command-line options on the restarted skeleton.

Reset optind to 1 at the restart label so options are re-parsed.

Affected schedulers: scx_simple, scx_central, scx_flatcg, scx_pair,
scx_sdt, scx_cpu0.

Signed-off-by: David Carlier <devnexen@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>