staging: comedi: always set hw_dev during auto-config

staging: comedi: always set hw_dev during auto-config

Auto-configuration (auto-attachment) of USB and PCI comedi devices all
goes through `comedi_auto_config_helper()`.  That is a good place to set
the comedi device's `hw_dev` pointer to the hardware `struct device` via
a call to `comedi_set_hw_dev(comedi_device, hardware_device)` as it may
obviate the need for the low-level comedi driver to make this call.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>