s390/compat: remove ptrace compat definitions from uapi header file

The compat definitions are not part of the uapi. So move them to
s390's private compat header file.

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