PM: fix compiler error of PPC dart_iommu

A dummy inline function of register_nosave_region_late was accidentally
removed by the recent PM patch that introduced suspend notifiers.
This elimination causes the following compiler error on PPC machines.

  CC      arch/powerpc/sysdev/dart_iommu.o
arch/powerpc/sysdev/dart_iommu.c: In function 'iommu_init_late_dart':
arch/powerpc/sysdev/dart_iommu.c:376: error: implicit declaration of function
'register_nosave_region_late'
make[1]: *** [arch/powerpc/sysdev/dart_iommu.o] Error 1
make: *** [arch/powerpc/sysdev] Error 2

This patch fixes the problem.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/suspend.h

@@ -125,6 +125,9 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
 static inline void register_nosave_region(unsigned long b, unsigned long e)
 {
 }
+static inline void register_nosave_region_late(unsigned long b, unsigned long e)
+{
+}
 #endif
 
 #endif /* _LINUX_SWSUSP_H */