m68k, m68knommu: Do not include linux/hardirq.h in asm/irqflags.h

Recent changes to header files made kernel compilation for m68k/m68knommu
fail with :
  CC      arch/m68knommu/kernel/asm-offsets.s
In file included from /archives/linux/git/arch/m68k/include/asm/system.h:2,
                 from include/linux/wait.h:25,
                 from include/linux/mmzone.h:9,
                 from include/linux/gfp.h:4,
                 from include/linux/irq.h:20,
                 from include/asm-generic/hardirq.h:12,
                 from /archives/linux/git/arch/m68k/include/asm/hardirq_no.h:17,
                 from /archives/linux/git/arch/m68k/include/asm/hardirq.h:2,
                 from include/linux/hardirq.h:10,
                 from /archives/linux/git/arch/m68k/include/asm/irqflags.h:5,
                 from include/linux/irqflags.h:15,
                 from include/linux/spinlock.h:53,
                 from include/linux/seqlock.h:29,
                 from include/linux/time.h:8,
                 from include/linux/timex.h:56,
                 from include/linux/sched.h:56,
                 from arch/m68knommu/kernel/asm-offsets.c:12:
/archives/linux/git/arch/m68k/include/asm/system_no.h: In function ‘__xchg’:
/archives/linux/git/arch/m68k/include/asm/system_no.h:79: error: implicit
+declaration of function ‘local_irq_save’
/archives/linux/git/arch/m68k/include/asm/system_no.h:101: error: implicit
+declaration of function ‘local_irq_restore’

Fix that

Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>

arch/m68k/include/asm/irqflags.h

@@ -2,7 +2,9 @@
 #define _M68K_IRQFLAGS_H
 
 #include <linux/types.h>
+#ifdef CONFIG_MMU
 #include <linux/hardirq.h>
+#endif
 #include <linux/preempt.h>
 #include <asm/thread_info.h>
 #include <asm/entry.h>