Bluetooth: mgmt: read/set system parameter definitions

This patch submits the corresponding kernel definitions to mgmt.h.
This is submitted before the implementation to avoid any conflicts in
values allocations.

Signed-off-by: Alain Michaud <alainm@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Yu Liu <yudiliu@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>