[PATCH] USB: gadgetfs: set "zero" flag for short control-IN response

This patch (as622) makes gadgetfs set the "zero" flag for control-IN
responses, when the length of the response is shorter than the length of
the request.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>