i386: Remove memset_chk-nonshared.S

Similar to memcpy, mempcpy, and memmove there is no need for an
specific memset_chk-nonshared.S.  It can be provided by
memset-ia32.S itself for static library.

Checked on i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>