staging: comedi: gsc_hpdi: remove pr_fmt() define

This driver no longer has any pr_{level} messages. Remove the pr_fmt().

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>