Bluetooth: Host: Fix bt_recv_thread_id assignment

The above mentioned fix attempts to detect the situation when
bt_att_req_alloc() is invoked on the same thread that runs
att_handle_rsp. It attempts to do so by noting the thread that
first ran bt_recv, assuming the same thread will house all calls
to bt_att_req_free. This turns out not to be correct. It is
evident from the call stack provided below that bt_att_req_free
can be called from other threads than the one that runs bt_recv.

Fixes: #43448

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>