staging: dgnc: delete dgnc_neo.* files

As the Neo devices were never actually supported by the driver, delete
the files that purported to control that type of device as they are not
needed.  This will let us shrink the driver a lot over time.

Cc: Lidza Louina <lidza.louina@gmail.com>
Cc: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>