Bluetooth: Use common error handling code in bt_init()

* Improve jump targets so that a bit of exception handling can be better
  reused at the end of this function.

* Adjust five condition checks.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>