USB: unusual_devs entry for Nokia N91

This patch (as745) adds an unusual_devs entry for the Nokia N91, just like
the entry for the N80 added a couple of weeks ago.  Apparently Nokia isn't
using very good firmware these days...

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