Bluetooth: hci_sync: remove unnecessary hci_conn_get in create_conn_sync

Bluetooth: hci_sync: remove unnecessary hci_conn_get in create_conn_sync

hci_conn_get() without already held reference is data race against
concurrent deletion.

In previous patches, the refcount has been changed to be taken before
starting the hci_sync task, so remove these extra get() + put() as they
are not needed.

Fixes: 12917f591cea ("Bluetooth: hci_conn: Fix null ptr deref in hci_abort_conn()")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>