USB: add asynchronous autosuspend/autoresume support

This patch (as1160b) adds support routines for asynchronous autosuspend
and autoresume, with accompanying documentation updates.  There
already are several potential users of this interface, and others are
likely to arise as autosuspend support becomes more widespread.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 400fa4c..44f2fc7 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -402,6 +402,7 @@
 #ifdef	CONFIG_PM
 	mutex_init(&dev->pm_mutex);
 	INIT_DELAYED_WORK(&dev->autosuspend, usb_autosuspend_work);
+	INIT_WORK(&dev->autoresume, usb_autoresume_work);
 	dev->autosuspend_delay = usb_autosuspend_delay * HZ;
 	dev->connect_time = jiffies;
 	dev->active_duration = -jiffies;