Bluetooth: Allow NRPA usage when connections are not supported

Currently CONFIG_BLUETOOTH_PRIVACY is defined as the ability to
generate RPAs, and it depends on CONFIG_BLUETOOTH_SMP. NRPA usage
however may be desirable even without these features (e.g. a
broadcaster-only device). Furthermore, if we are using RPA based
privacy we should be using that instead of NRPA even when doing
non-connectable advertising.

This patch leaves out the option of advertising with the Identity
Address when non-connectable, however if we get a use case for that we
could consider adding a BT_LE_ADV_OPT_ID_ADDR to force using it.

Change-Id: I0502323aec15eefad1a729c393c707108d4cf758
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>