Bluetooth: Host: Add `const` to `bt_conn_index`

The `bt_conn_index` simply returns the index
of a `bt_conn` struct. There is no reason why
such a function should not use `const`.

Not using `const` will make other lookup/index
functions that perhaps relies on the bt_conn index
unable to use `const` as well.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>
3 files changed