staging: comedi: das08: rename and rewrite DAS08_EOC
The `DAS08_EOC` macro contains a mask for the "end of A/D conversion"
bit in the status register. The logic is reverse sense in that the bit
is set to 1 while the conversion is in progress and set to 0 when the
conversion is complete. Rename the macro to `DAS08_STATUS_AI_BUSY` and
add a comment. Also make use of the `BIT()` macro to define the value.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>