i386: Remove libc-do-syscall from sysdep-dl-routines [BZ #28936]

Remove libc-do-syscall from sysdep-dl-routines added by:

commit 3b33d6ed
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Sun Jan 8 11:38:23 2017 -0200

    Rework -fno-omit-frame-pointer support on i386

and use auto-generated io/rtld-libc-do-syscall.os instead.  This fixes
BZ #28936.