staging: comedi: pcl818: remove unused RTC dma support

All the RTC dma support code in this driver is #ifdef'ed out.

Remove the unused code to assist in cleaning up this driver.
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>