staging: comedi: das800: tidy up das800_ai_do_cmdtest()

For aesthetic reasons, move some of the local variables to the place
they are actually used. Also, rename the CamelCase 'startChan' local
variable.

Remove the unnecessary '()' around the variables passed in the
i8253_cascade_ns_to_timer_2div() call.

Add a local variable, 'next', to hold the cmd->chanlist[i] value
used in the loop that checks the channel/gain list.

Replace the comedi_error() with dev_dbg() and shorten the messages
a bit.

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>