Hibernation: do not try to mark invalid PFNs as nosave

Hibernation: do not try to mark invalid PFNs as nosave

On some systems some PFNs reported by the early initialization code as 'nosave'
may be invalid. =A0If we try to set the corresponding bits in the hibernation
bitmap, BUG_ON() in memory_bm_find_bit() will be triggered and the system
won't be able to boot (cf. https://bugzilla.novell.com/show_bug.cgi?id=296242).

Prevent this from happening by verifying if the 'nosave' PFNs are valid in
mark_nosave_pages().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>