staging: comedi: usbduxfast: Move usb_driver (*probe) into comedi_driver

Currently, the usb_driver (*probe) locates a free place in the static
usbduxfast array to use for the private data in this driver. It then
does some initial setup of the usb device and allocates the buffers
needed. The firmware for the device is then requested and uploaded
before calling comedi_usb_auto_config() to allow the comedi core to
complete the (*auto_attach) of the device.

Move the bulk of the (*probe) into the comedi_driver (*auto_attach).
This allows the private data to be kzalloc'ed. We can then remove the
static array along with the semaphore that protected it.

This also removes the 16 attached devices limitation.

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>