Bluetooth: Coding style fix

1. Add space when needed;
2. Block comments style fix;
3. Move open brace '{' following function definitions to the next line;
4. Remove unnecessary braces '{}' for single statement blocks.

Signed-off-by: Meng Yu <yumeng18@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>