platform/x86: think-lmi: Fix memory leaks when parsing ThinkStation WMI strings

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

platform/x86: think-lmi: Fix memory leaks when parsing ThinkStation WMI strings

My previous commit introduced a memory leak where the item allocated

from tlmi_setting was not freed.

This commit also renames it to avoid confusion with the similarly name

variable in the same function.