usb: misc: ljca: Fix enumeration error on Dell Latitude 9420

Not all LJCA chips implement SPI and on chips without SPI reading
the SPI descriptors will timeout.

On laptop models like the Dell Latitude 9420, this is expected behavior
and not an error.

Modify the driver to continue without instantiating a SPI auxbus child,
instead of failing to probe() the whole LJCA chip.

Fixes: acd6199f

 ("usb: Add support for Intel LJCA device")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Wentong Wu <wentong.wu@intel.com>
Link: https://lore.kernel.org/r/20231104175104.38786-1-hdegoede@redhat.com
Link: https://lore.kernel.org/r/20231121203205.223047-1-hdegoede@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>