staging: comedi: das16: board is not a PCI device

The DAS16 board is an ISA device not a PCI device. For aesthetics, use
dma_{alloc,free}_coherent() to allocate and free the DMA buffers instead
of the PCI versions.

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>