PM: Separate hibernation code from suspend code

[ With Johannes Berg <johannes@sipsolutions.net> ]

Separate the hibernation (aka suspend to disk code) from the other suspend
code.  In particular:

 * Remove the definitions related to hibernation from include/linux/pm.h
 * Introduce struct hibernation_ops and a new hibernate() function to hibernate
   the system, defined in include/linux/suspend.h
 * Separate suspend code in kernel/power/main.c from hibernation-related code
   in kernel/power/disk.c and kernel/power/user.c (with the help of
   hibernation_ops)
 * Switch ACPI (the only user of pm_ops.pm_disk_mode) to hibernation_ops

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Greg KH <greg@kroah.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 34b4354..5138148 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -25,12 +25,7 @@
  */
 #define SPARE_PAGES	((1024 * 1024) >> PAGE_SHIFT)
 
-extern int pm_suspend_disk(void);
-#else
-static inline int pm_suspend_disk(void)
-{
-	return -EPERM;
-}
+extern struct hibernation_ops *hibernation_ops;
 #endif
 
 extern int pfn_is_nosave(unsigned long);