staging: comedi: quatech_daqp_cs: tidy up command register bits

For aesthetics, move the bit defines for this register and use the
BIT macro to define the bits. Define a macro for the scanrate bits
and use it to remove the CamelCase. Rename the defines to match the
register.

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>