Bluetooth: Fix hci_connect error return values

The hci_connect function should either return a valid hci_conn pointer
or a ERR_PTR() but never NULL. This patch fixes the two places where
hci_conn_add failures would have caused a NULL return. The only reason
for failure with hci_conn_add is memory allocation so ENOMEM seems to be
a good choice here.

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

net/bluetooth/hci_conn.c

···
 	if (!acl) {
 		acl = hci_conn_add(hdev, ACL_LINK, dst);
 		if (!acl)
-			return NULL;
+			return ERR_PTR(-ENOMEM);
 	}
 
 	hci_conn_hold(acl);
···
 		sco = hci_conn_add(hdev, type, dst);
 		if (!sco) {
 			hci_conn_put(acl);
-			return NULL;
+			return ERR_PTR(-ENOMEM);
 		}
 	}