tpm xen: drop unneeded chip variable

The call that used chip was dropped in 1f0f30e404b3. Drop the
leftover declaration and initialization.

Signed-off-by: Julia Lawall <[e-mail]>
Reviewed-by: Jarkko Sakkinen <[e-mail]>
Signed-off-by: Jarkko Sakkinen <[e-mail]>

drivers/char/tpm/xen-tpmfront.c

···
 		const struct xenbus_device_id *id)
 {
 	struct tpm_private *priv;
-	struct tpm_chip *chip;
 	int rv;
 
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
···
 
 	rv = setup_ring(dev, priv);
 	if (rv) {
-		chip = dev_get_drvdata(&dev->dev);
 		ring_free(priv);
 		return rv;
 	}