s390/abs_lowcore: Include linux/smp.h for get_cpu() and put_cpu()

Add missing include of <linux/smp.h> in abs_lowcore.h to provide
declarations for get_cpu() and put_cpu() used in the code.

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

Author: Vasily Gorbik

arch/s390/include/asm/abs_lowcore.h

@@ -2,6 +2,7 @@
 #ifndef _ASM_S390_ABS_LOWCORE_H
 #define _ASM_S390_ABS_LOWCORE_H
 
+#include <linux/smp.h>
 #include <asm/lowcore.h>
 
 #define ABS_LOWCORE_MAP_SIZE	(NR_CPUS * sizeof(struct lowcore))