s390: Remove S390_lowcore

With all users gone, remove S390_lowcore.
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/lowcore.h

@@ -213,8 +213,6 @@ struct lowcore {
 	__u8	pad_0x1900[0x2000-0x1900];	/* 0x1900 */
 } __packed __aligned(8192);
 
-#define S390_lowcore (*((struct lowcore *) 0))
-
 static __always_inline struct lowcore *get_lowcore(void)
 {
 	return NULL;