Bluetooth: Add helper to get HCI channel of a socket

We'll need to have access to which HCI channel a socket is bound to, in
order to manage pending mgmt commands in clean way. This patch adds a
helper for the purpose.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --cc include/net/bluetooth/bluetooth.h
Simple merge

diff --cc net/bluetooth/hci_sock.c
Simple merge