LDAP: Add the NotAllowed returned error for ldapType property

Implementation should not allow to change the ldap type once the
D-Bus object gets created, To support this adding the "NotAllowed"
error in the property return errors.

Change-Id: I6cfc1255d87e12548a1b474e12ee52cbb7f4eb8e
Signed-off-by: Ratan Gupta <ratagupt@linux.vnet.ibm.com>
diff --git a/xyz/openbmc_project/User/Ldap/Config.interface.yaml b/xyz/openbmc_project/User/Ldap/Config.interface.yaml
index 42c7126..227760a 100644
--- a/xyz/openbmc_project/User/Ldap/Config.interface.yaml
+++ b/xyz/openbmc_project/User/Ldap/Config.interface.yaml
@@ -52,8 +52,11 @@
           OpenLdap. It's just an indication for the LDAP stack running on
           the BMC, in case the app is implemented in such a way that it has
           to react differently for AD vs openldap.
+          This property is readonly, Once the D-Bus object gets created then
+          this property should not be modifiable.
       errors:
         - xyz.openbmc_project.Common.Error.InternalFailure
+        - xyz.openbmc_project.Common.Error.NotAllowed
     - name: GroupNameAttribute
       type: string
       description: >