staging: comedi: addi_apci_3xxx: refactor i_APCI3XXX_InsnWriteAnalogOutput()

Rename the CamelCase local variables.

The comedi core validates the insn->chanspec to make sure the channel
number and range are valid for the subdevice. The extra checks in this
function are not required.

(*insn_write) functions are supposed to write all the data passed
in the data pointer (insn->n values) then return the number of data
values written of an errno. Fix this function to work like the core
expects.

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>