tpm: return -ENODEV if np is not set

device_node np contains a garbage value from the stack and it
is only set if chip->dev.parent->of_node is not null.  Thus the
check for a null np won't spot a garbage value of np from the
stack if chip->dev.parent->of_node is null and if np contains
an garbage non-null value.

I believe the correct fix is to return -ENODEV if and only if
chip->dev.parent->of_node is null.

Found with static analysis by CoverityScan, CID 1377755

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm_of.c

@@ -31,7 +31,7 @@ int tpm_read_log_of(struct tpm_chip *chip)
 	log = &chip->log;
 	if (chip->dev.parent->of_node)
 		np = chip->dev.parent->of_node;
-	if (!np)
+	else
 		return -ENODEV;
 
 	sizep = of_get_property(np, "linux,sml-size", NULL);