Bluetooth: Restrict loading of long term keys to LE capable controllers

Loading long term keys into a BR/EDR only controller make no sense.
The kernel would never use any of these keys. So instead of allowing
userspace to waste memory, reject such operation with a not supported
error message.

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