Bluetooth: Refactor buffer HCI user data

To accommodate for ACL user data move the HCI command/event data into
its own struct and put it inside a union in bt_buf.

Change-Id: I680500b15709d14b1e9f70ced88664d607a6568c
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
3 files changed