Bluetooth: remove set but not used variable 'smp'

Fixes gcc '-Wunused-but-set-variable' warning:

net/bluetooth/smp.c: In function 'smp_irk_matches':
net/bluetooth/smp.c:505:18: warning: variable 'smp' set but not used [-Wunused-but-set-variable]

net/bluetooth/smp.c: In function 'smp_generate_rpa':
net/bluetooth/smp.c:526:18: warning: variable 'smp' set but not used [-Wunused-but-set-variable]

It is not used since commit 28a220aa ("bluetooth: switch
to AES library")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>