Bluetooth: Rename smp->local_rr into smp->local_rand

The variable for the out-of-band random number was badly named and
with that confusing. Just rename it to local_rand so it is clear
what value it represents.

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