staging: comedi: addi-data: remove unused 'i_Dma' present flag

None of the addi-data drivers that still use the "common" code support
dma. Remove the unnecessaary boardinfo and private data flags.

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>