This patch adds a bit-array to the hub driver's private data structure,
used for storing the contents of the hub's interrupt status message.  That
message indicates which ports have events pending (and whether the hub
itself has events pending).  By only polling the status of the ports
listed in the bit-array we can save a fair amount of overhead in hub
communication.

(The #error test added to hub.h is a little awkward, but it's purely
precautionary -- it won't matter until someone decides to support hubs
with more than 31 ports!)

Also included in the patch, since this seemed the perfect opportunity for
it, is Byron's suggestion for handling hub events in the order in which
they were received.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>