[PATCH] s390: fix locking in __chp_add() and s390_subchannel_remove_chpid()

Fix locking in __chp_add() and s390_subchannel_remove_chpid(): Need to
disable/enable because they are always called from a thread (and not
directly from a machine check...)

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>