[S390] irq: merge irq.c and s390_ext.c

Merge irq.c and s390_ext.c into irq.c. That way all external interrupt
related functions are together.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/fault.c

@@ -34,7 +34,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/system.h>
 #include <asm/pgtable.h>
-#include <asm/s390_ext.h>
+#include <asm/irq.h>
 #include <asm/mmu_context.h>
 #include <asm/compat.h>
 #include "../kernel/entry.h"