Bluetooth: mgmt: Add commands for runtime configuration

This adds the required read/set commands for runtime configuration. Even
while currently no parameters are specified, the commands are made
available.

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