selftest/seccomp: Fix the flag name SECCOMP_FILTER_FLAG_TSYNC

Rename SECCOMP_FLAG_FILTER_TSYNC to SECCOMP_FILTER_FLAG_TSYNC to match
the UAPI.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Will Drewry <wad@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>