darwin: improve support for auto-detaching a kernel driver

darwin: improve support for auto-detaching a kernel driver

This commit improves the code around auto attach/detach of a kernel driver:

 - Log a warning when a driver can not be auto-detached and continue when claiming an
   interface. It could be the case that the interface has no driver attached or that
   the claim will still succeed.

 - Log a warning if the driver can not be auto-attached and return success when
   releasing an interface. The operation did complete successfully but the
   re-enumeration may have failed. This can be discovered on the next device
   access.

Signed-off-by: Nathan Hjelm <hjelmn@google.com>