PM: Fix pm_notifiers during user mode hibernation

Snapshot device is opened with O_RDONLY during suspend and O_WRONLY durig
resume.  Make sure we also call notifiers with correct parameter telling
them what we are really doing.

Signed-off-by: Andrey Borzenkov <arvidjaar@mail.ru>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg KH <gregkh@suse.de>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>