staging: dgnc: remove error message task

TODO file lists task to remove unnecessary error messages. There are
no unnecessary error messages in the driver, this must have been done
already.

Remove task from TODO file.
Signed-off-by: NTobin C. Harding <me@tobin.cc>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/TODO

 * remove unnecessary comments
-* remove unnecessary error messages. Example kzalloc() has its
-  own error message. Adding an extra one is useless.
 * there is a lot of unnecessary code in the driver. It was
   originally a standalone driver. Remove unneeded code.