staging: comedi: dt282x: convert printk() in dt282x_attach to a dev_err()

Convert this printk message into a dev_err().

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