[S390] remove code for oldselect system call

The system call isn't wired up on s390. Just delete the dead code.
Also we use the common code sys_ptrace system call, so the sys_ptrace
declaration is pointless is well.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>