staging: comedi: pcmuio: tidy up pcmuio_attach()

Clean up the local variables, 'sdev_no' and 'asic' are both used in
simple for () loops. Use the local variable 'i' for both cases. The
'n_subdevs' variable is only used in one place, just remove it.

For aesthetics, add some whitespace to the subdevice init and reorder
it to follow the more typical style in comedi drivers.

Remove the unnecessary init of s->len_chanlist for subdevices that do
not support async commands (interrupts). The core will default it to
the correct value.

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>