[PATCH] powerpc/pseries: dlpar-add crash on null pointer deref

This fixes a crash on null-pointer deref during dlpar slot addition.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
(cherry picked from 1c87c0f84943fbbc91826967ff4fea1b059a526f commit)