Relocate the twin mce functions to arch/x86/mm/pat/set_memory.c
file where they belong.

While at it, fixup a function name in a comment.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
[sfr: gate {set,clear}_mce_nospec() by CONFIG_X86_64]
Link: https://lore.kernel.org/r/165272527328.90175.8336008202048685278.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>