[PATCH] s390: system call speedup part 1.

[PATCH] s390: system call speedup part 1.

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

The purpose of this is to speed up system calls on s390.  I managed to
squeeze about 65 cycles from each system call.  This improved e.g.  getpid()
from 232 to 157 cycles.  As a nice side-effect it simplified the uaccess
functions considerably.