usb: hub: rename khubd to hub_wq in documentation and comments

USB hub has started to use a workqueue instead of kthread. Let's update
the documentation and comments here and there.

This patch mostly just replaces "khubd" with "hub_wq". There are only few
exceptions where the whole sentence was updated. These more complicated
changes can be found in the following files:

	   Documentation/usb/hotplug.txt
	   drivers/net/usb/usbnet.c
	   drivers/usb/core/hcd.c
	   drivers/usb/host/ohci-hcd.c
	   drivers/usb/host/xhci.c

Signed-off-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/fhci-hcd.c b/drivers/usb/host/fhci-hcd.c
index 1cf68eaf2..a1a1ef5 100644
--- a/drivers/usb/host/fhci-hcd.c
+++ b/drivers/usb/host/fhci-hcd.c
@@ -360,12 +360,12 @@
 	hcd->state = HC_STATE_RUNNING;
 
 	/*
-	 * From here on, khubd concurrently accesses the root
+	 * From here on, hub_wq concurrently accesses the root
 	 * hub; drivers will be talking to enumerated devices.
-	 * (On restart paths, khubd already knows about the root
+	 * (On restart paths, hub_wq already knows about the root
 	 * hub and could find work as soon as we wrote FLAG_CF.)
 	 *
-	 * Before this point the HC was idle/ready.  After, khubd
+	 * Before this point the HC was idle/ready.  After, hub_wq
 	 * and device drivers may start it running.
 	 */
 	fhci_usb_enable(fhci);