Bluetooth: Remove unnecessary indentation in unpair_device()

Instead of doing all of the LE-specific handling in an else-branch in
unpair_device() create a 'done' label for the BR/EDR branch to jump to
and then remove the else-branch completely.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>