staging: comedi: use inlines for PCI/USB auto config

Apart from the somewhat unnecessary `BUG_ON()` calls,
`comedi_pci_auto_config()` and `comedi_usb_auto_config()` are just
one-line wrappers around `comedi_auto_config()`, and
`comedi_pci_auto_unconfig()` and `comedi_usb_auto_unconfig()` are just
one-line wrappers around `comedi_auto_unconfig()`.  Convert them to
inline functions and remove the `BUG_ON()` calls.

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