driver core: per-subsystem multithreaded probing

Make multithreaded probing work per subsystem instead of per driver.

It doesn't make much sense to probe the same device for multiple drivers in
parallel (after all, only one driver can bind to the device).  Instead, create
a probing thread for each device that probes the drivers one after another. 
Also make the decision to use multi-threaded probe per bus instead of per
device and adapt the pci code.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/device.h b/include/linux/device.h
index 7f63d4d..eb1fff0 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -80,6 +80,7 @@
 	int (*resume)(struct device * dev);
 
 	unsigned int drivers_autoprobe:1;
+	unsigned int multithread_probe:1;
 };
 
 extern int __must_check bus_register(struct bus_type * bus);
@@ -139,8 +140,6 @@
 	void	(*shutdown)	(struct device * dev);
 	int	(*suspend)	(struct device * dev, pm_message_t state);
 	int	(*resume)	(struct device * dev);
-
-	unsigned int multithread_probe:1;
 };