Staging: add Support for Quatech ESU2-100 USB 2.0 8-port serial adaptor

The patch is of the "works as far as it goes" variety, in that the
module compiles and loads, the device nodes are registered and the unit
switched on, but nothing actually works. On the other hand, it doesn't
panic the kernel, as far as I know.

Signed-off-by: Richard Ash <richard@audacityteam.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>