Bluetooth: hci_sync: cancel cmd_timer if hci_open failed

If a command is already sent, we take care of freeing it, but we
also need to cancel the timeout as well.

Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>