staging: comedi: don't check driver->auto_attach

There is no need for `comedi_pci_auto_config()` and
`comedi_usb_auto_config()` to check that `driver->auto_attach` is
non-null before calling `comedi_auto_attach()` as this check is done by
`comedi_auto_config()` itself (actually by
`comedi_auto_config_wrapper()`).  Remove the unnecessary checks.

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