PM: Move definition of struct pm_ops to suspend.h

Move the definition of 'struct pm_ops' and related functions from <linux/pm.h>
to <linux/suspend.h> .

There are, at least, the following reasons to do that:
* 'struct pm_ops' is specifically related to suspend and not to the power
  management in general.
* As long as 'struct pm_ops' is defined in <linux/pm.h>, any modification of it
  causes the entire kernel to be recompiled, which is unnecessary and annoying.
* Some suspend-related features are already defined in <linux/suspend.h>, so it
  is logical to move the definition of 'struct pm_ops' into there.
* 'struct hibernation_ops', being the hibernation-related counterpart of
  'struct pm_ops', is defined in <linux/suspend.h> .

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>