USB: Move private hub declarations out of public header file

This patch (as809b) moves the declaration of the hub driver's private
data structure from hub.h into the hub.c source file.  Lots of other
files import hub.h; they have no need to know about the details of the
hub driver's private data.

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