platform/x86: think-lmi: Fix reference leak

In the Linux kernel, the following vulnerability has been resolved:

platform/x86: think-lmi: Fix reference leak

If a duplicate attribute is found using kset_find_obj(), a reference

to that attribute is returned which needs to be disposed accordingly

using kobject_put(). Move the setting name validation into a separate

function to allow for this change without having to duplicate the

cleanup code for this setting.

As a side note, a very similar bug was fixed in

commit 7295a996fdab ("platform/x86: dell-sysman: Fix reference leak"),

so it seems that the bug was copied from that driver.

Compile-tested only.