tpm: fix compat 'ppi' link handling in tpm_chip_register()

__compat_only_sysfs_link_entry_to_kobj() was unconditionally called for
TPM1 chips, which caused crash on Acer C720 laptop where DSM for the
ACPI object did not exist.

There are two reasons for unwanted behavior:

* The code did not check whether
  __compat_only_sysfs_link_entry_to_kobj() returned -ENOENT. This is
  OK. It just meanst that ppi is not available.
* The code did not clean up properly. Compat link should added only
  after all other init is done.

This patch sorts out these issues.

Fixes: 9b774d5
Reported-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jeremiah Mahler <jmmahler@gmail.com>
Acked-by: Peter Huewe <PeterHuewe@gmx.de>

drivers/char/tpm/tpm-chip.c

@@ -226,21 +226,23 @@ int tpm_chip_register(struct tpm_chip *chip)
 	if (rc)
 		goto out_err;
 
-	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
-		rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
-							    &chip->dev.kobj,
-							    "ppi");
-		if (rc)
-			goto out_err;
-	}
-
 	/* Make the chip available. */
 	spin_lock(&driver_lock);
 	list_add_tail_rcu(&chip->list, &tpm_chip_list);
 	spin_unlock(&driver_lock);
 
 	chip->flags |= TPM_CHIP_FLAG_REGISTERED;
 
+	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
+		rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
+							    &chip->dev.kobj,
+							    "ppi");
+		if (rc && rc != -ENOENT) {
+			tpm_chip_unregister(chip);
+			return rc;
+		}
+	}
+
 	return 0;
 out_err:
 	tpm1_chip_unregister(chip);