s390/kprobes,ptrace: open code struct per_reg

Open code struct per_regs within kprobes and ptrace code, since at both
locations a struct per_regs is passed to __local_ctl_load() and
__local_ctl_store() which prevents to implement type checking for both
functions.

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>