x86/pat: Remove the unused set_pages_array_wt() function

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  623dffb2 ("x86/mm/pat: Add set_memory_wt() for Write-Through type")

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Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220223072852.616143-1-hch@lst.de