Bluetooth: Make AES crypto context private to SMP

Now that we have per-adapter SMP data thanks to the root SMP L2CAP
channel we can take advantage of it and attach the AES crypto context
(only used for SMP) to it. This means that the smp_irk_matches() and
smp_generate_rpa() function can be converted to internally handle the
AES context.

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