Bluetooth: Fix generation of non-resolvable private addresses

When the host decides to use a non-resolvable private address, it
must ensure that this generated address does not match the public
address of the controller. Add an extra check to ensure this required
behavior.

In addition rename the variable from urpa to nrpa and fix all of the
comments in the code that use the term unresolvable instead of the
term non-resolvable as used in the Bluetooth specification.

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