Bluetooth: Assign the channel early when binding HCI sockets

Assignment of the hci_pi(sk)->channel should be done early when binding
the HCI socket. This avoids confusion with the RAW channel that is used
for legacy access.

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