Bluetooth: btsdio: Free driver data on SDIO shutdown

Instead of waiting for the hdev object to get freed we now free the
private driver-internal data on SDIO shutdown. This allows us to remove
the obsolete hci-destruct callback and free our data object right away
after calling hci_unregister_dev(). The HCI-core does not call any
callbacks after this so we are never called again and can safely exit
the module.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>