Bluetooth: Use kzalloc instead of kmalloc/memset

Use kzalloc rather than kmalloc followed by memset with 0.

Generated by: scripts/coccinelle/api/alloc/kzalloc-simple.cocci

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>