[S390] hardirq: remove pointless header file includes

Remove a couple of pointless header file includes.
Fixes a compile bug caused by header file include dependencies with
"irq: Add tracepoint to softirq_raise" within linux-next.

Reported-by: Sachin Sant <sachinp@in.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[ cherry-picked from the s390 tree to fix "2bf2160: irq: Add tracepoint to softirq_raise" ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/s390/include/asm/hardirq.h

@@ -12,10 +12,6 @@
 #ifndef __ASM_HARDIRQ_H
 #define __ASM_HARDIRQ_H
 
-#include <linux/threads.h>
-#include <linux/sched.h>
-#include <linux/cache.h>
-#include <linux/interrupt.h>
 #include <asm/lowcore.h>
 
 #define local_softirq_pending() (S390_lowcore.softirq_pending)