Build failure in v4.4.y-queue

Building s390:defconfig ... failed -------------- Error log: arch/s390/kernel/smp.c: In function 'smp_call_ipl_cpu': arch/s390/kernel/smp.c:363:23: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types] struct lowcore *lc = pcpu_devices->lowcore; ^~~~~~~~~~~~ arch/s390/kernel/smp.c:366:6: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types] lc = &S390_lowcore; ^ arch/s390/kernel/smp.c:369:11: error: dereferencing pointer to incomplete type 'struct lowcore'