s390/setup: make use of system_ctl_load()

s390/setup: make use of system_ctl_load()

Use system_ctl_load() instead of local_ctl_load() to reflect that
control register changes are supposed to be global.

Even though setup_cr() was ok, note that the usage of local_ctl_load()
would have been wrong, if it would have happened after the control
register save area was initialized: only local control register contents
would have been changed, but wouldn't be used for new CPUs.

With using system_ctl_load() the caller doesn't need to take care.

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