staging: comedi: dt9812: Resolves sparse endian warnings.

Resolves warnings from the "sparse" checker of the form "warning: cast to
restricted __le??".

Signed-off-by: Shaun Laing <shaun@xresource.ca>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>