Bluetooth: Track Secure Connections support of remote devices

It is important to know if Secure Connections support has been enabled
for a given remote device. The information is provided in the remote
host features page. So track this information and provide a simple
helper function to extract the status.

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