staging: comedi: cb_pcidda: cleanup cb_pcidda_ao_winsn()

For aesthetic reasons, rename the function to help when searching
for 'insn_write' functions.

Remove the obvious comments and fix the return from the function.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>