Bluetooth: fix coccicheck warnings debugfs

Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
for debugfs files.

Reported-by: Abaci <Robot&lt;abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Zhong <abaci-bugfix@linux.alibaba.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>