staging: comedi: poc: remove obsolete driver

The DAC02 board, which is the only board supported by this driver, now
has its own comedi driver (dac02).

Remove this obsolete 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>