Bluetooth: Add smp_sufficient_security helper function

This function is needed both by the smp_conn_security function as well
as upcoming code to check for the security requirements when receiving
an L2CAP connect request over LE.

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

diff --cc net/bluetooth/smp.c
Simple merge

diff --cc net/bluetooth/smp.h
Simple merge