HSI: nokia-modem: fix error return code

Return a negative error code on failure.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier ret; expression e1,e2;
@@
(
if (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/hsi/clients/nokia-modem.c

@@ -200,6 +200,7 @@ static int nokia_modem_probe(struct device *dev)
 	modem->ssi_protocol = hsi_new_client(port, &ssip);
 	if (!modem->ssi_protocol) {
 		dev_err(dev, "Could not register ssi-protocol device\n");
+		err = -ENOMEM;
 		goto error2;
 	}