Bluetooth: Remove unneeded bt_cb(skb)->channel variable

The bt_cb(skb)->channel was only needed to make hci_send_to_sock() be
used for HCI raw and control sockets. Since they have now separate sending
functions this is no longer needed.

Signed-off-by: Marcel Holtmann <[e-mail]>
Signed-off-by: Johan Hedberg <[e-mail]>

include/net/bluetooth/bluetooth.h

···
 	__u16 tx_seq;
 	__u8 retries;
 	__u8 sar;
-	unsigned short channel;
 	__u8 force_active;
 };
 #define bt_cb(skb) ((struct bt_skb_cb *)((skb)->cb))

net/bluetooth/mgmt.c

···
 	if (!skb)
 		return -ENOMEM;
 
-	bt_cb(skb)->channel = HCI_CHANNEL_CONTROL;
-
 	hdr = (void *) skb_put(skb, sizeof(*hdr));
 	hdr->opcode = cpu_to_le16(event);
 	if (hdev)