USB: re-enable interface after driver unbinds

This patch (as1197) fixes an error introduced recently.  Since a
significant number of devices can't handle Set-Interface requests, we
no longer call usb_set_interface() when a driver unbinds from an
interface, provided the interface is already in altsetting 0.  However
the interface still does get disabled, and the call to
usb_set_interface() was the only thing re-enabling it.  Since the
interface doesn't get re-enabled, further attempts to use it fail.

So the patch adds a call to usb_enable_interface() when a driver
unbinds and the interface is in altsetting 0.  For this to work
right, the interface's endpoints have to be re-enabled but their
toggles have to be left alone.  Therefore an additional argument is
added to usb_enable_endpoint() and usb_enable_interface(), a flag
indicating whether or not the endpoint toggles should be reset.

This is a forward-ported version of a patch which fixes Bugzilla
#12301.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: David Roka <roka@dawid.hu>
Reported-by: Erik Ekman <erik@kryo.se>
Tested-by: Erik Ekman <erik@kryo.se>
Tested-by: Alon Bar-Lev <alon.barlev@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index c082156..dcfc072 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -362,7 +362,7 @@
 	dev->ep0.desc.bLength = USB_DT_ENDPOINT_SIZE;
 	dev->ep0.desc.bDescriptorType = USB_DT_ENDPOINT;
 	/* ep0 maxpacket comes later, from device descriptor */
-	usb_enable_endpoint(dev, &dev->ep0);
+	usb_enable_endpoint(dev, &dev->ep0, true);
 	dev->can_submit = 1;
 
 	/* Save readable and stable topology id, distinguishing devices