wmi-acer: Use kzalloc to handle _WDG result

wmi-acer: Use kzalloc to handle _WDG result

Currently, we use acpi_allocate_buffer() to produce and store the
results of our initial call to _WDG. Unfortunately, it would seem
that memory is liable to be overwritten on some systems by later
calls into ACPI (e.g. such as calling acpi_evaluate_object()).

So fix this by:

A) Allocating our own memory to hold the GUIDs from _WDG
B) Copy the output buffer from _WDG to our allocated memory
C) Free the original buffer, and keep our local copy