Bluetooth: hci_core: Avoid mixing up req_complete and req_complete_skb

In commit 44d27137 ("Bluetooth: Compress the size of struct
hci_ctrl") we squashed down the size of the structure by using a union
with the assumption that all users would use the flag to determine
whether we had a req_complete or a req_complete_skb.

Unfortunately we had a case in hci_req_cmd_complete() where we weren't
looking at the flag.  This can result in a situation where we might be
storing a hci_req_complete_skb_t in a hci_req_complete_t variable, or
vice versa.

During some testing I found at least one case where the function
hci_req_sync_complete() was called improperly because the kernel thought
that it didn't require an SKB.  Looking through the stack in kgdb I
found that it was called by hci_event_packet() and that
hci_event_packet() had both of its locals "req_complete" and
"req_complete_skb" pointing to the same place: both to
hci_req_sync_complete().

Let's make sure we always check the flag.

For more details on debugging done, see <http://crbug.com/588288

>.

Fixes: 44d27137 ("Bluetooth: Compress the size of struct hci_ctrl")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>