staging: comedi: dt3000: remove empty 'else' code

There are a number of:

	} else {
		/* not supported */
	}

cases in this driver. Remove them.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>