staging: comedi: dt9812: remove pr_fmt()

There are no pr_{level} messages in this driver. Remove the pr_fmt().

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>