USB: add ep->enable

This patch (as944) adds an explicit "enabled" field to the
usb_host_endpoint structure and uses it in place of the current
mechanism.  This is merely a time-space tradeoff; it makes checking
whether URBs may be submitted to an endpoint simpler.  The existing
mechanism is efficient when converting urb->pipe to an endpoint
pointer, but it's not so efficient when urb->ep is used instead.

As a side effect, the procedure for enabling an endpoint is now a
little more complicated.  The ad-hoc inline code in usb.c and hub.c
for enabling ep0 is now replaced with calls to usb_enable_endpoint,
which is no longer static.

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

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index f7b337f..c8a01f6 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1999,7 +1999,7 @@
 {
 	usb_disable_endpoint(udev, 0 + USB_DIR_IN);
 	usb_disable_endpoint(udev, 0 + USB_DIR_OUT);
-	udev->ep_in[0] = udev->ep_out[0] = &udev->ep0;
+	usb_enable_endpoint(udev, &udev->ep0);
 }
 
 #define usb_sndaddr0pipe()	(PIPE_CONTROL << 30)