iucv: convert cpu notifier to return encapsulate errno value

By the previous modification, the cpu notifier can return encapsulate
errno value.  This converts the cpu notifiers for iucv.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>