PM: Free memory bitmaps if opening /dev/snapshot fails

When opening /dev/snapshot device, snapshot_open() creates memory
bitmaps which are freed in snapshot_release(). But if any of the
callbacks called by pm_notifier_call_chain() returns NOTIFY_BAD, open()
fails, snapshot_release() is never called and bitmaps are not freed.
Next attempt to open /dev/snapshot then triggers BUG_ON() check in
create_basic_memory_bitmaps(). This happens e.g. when vmwatchdog module
is active on s390x.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: stable@kernel.org

kernel/power/user.c

@@ -113,8 +113,10 @@ static int snapshot_open(struct inode *inode, struct file *filp)
 		if (error)
 			pm_notifier_call_chain(PM_POST_RESTORE);
 	}
-	if (error)
+	if (error) {
+		free_basic_memory_bitmaps();
 		atomic_inc(&snapshot_device_available);
+	}
 	data->frozen = 0;
 	data->ready = 0;
 	data->platform_support = 0;