Bluetooth: Restrict loading of link keys to BR/EDR capable controllers

Loading link keys into a LE 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>