[PATCH] swsusp: fix memory shrinker

Fix a bug in the swsusp's memory shrinker that causes some systems using
highmem to refuse to suspend to disk if image_size is set above 1/2 of
available RAM.

Special thanks to Jiri Slaby for reporting the problem and assistance in
debugging it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>