[S390] ipc: call generic sys_ipc demultiplexer

Call generic IPC demultiplexer instead of having a nearly identical
s390 variant. Also make sure that native and compat handling now have
the same behaviour.

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