Bluetooth: Remove only enabled entries with Remove Device command

The Remove Device mgmt command is supposed to undo what the Add Device
command does. An entry added by Add Device cannot have the
HCI_AUTO_CONN_DISABLED auto_connect value, so we should treat this as an
invalid entry to remove. This patch adds the necessary pieces to the
Remove Device command handler so that it only removes entries which were
added by Add Device.

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