Bluetooth: Move struct hci_sec_filter next to its user

There is only single location using struct hci_sec_filter and with
that there is no point in putting this declaration into a global
header file. So move it right next to its user and make the code
a lot more simpler.

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