staging: dgnc: remove unnecessary comments

TODO file lists task to remove unnecessary comments.

Make initial attempt at removing unnecessary comments. Choose not to
be to vicious in removal. We can remove more once the driver is
cleaned up/tested some more.

For functions with internal linkage, reduce the function comment where
possible. For functions with external linkage, migrate the function
comment to kernel doc format.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>