x86/pat: Do not compile stubbed functions when X86_PAT is off

Those are already provided by linux/io.h as stubs.

The conflict remains invisible until someone would pull linux/io.h into
memtype.c. This fixes a build error when this file is used outside of
the kernel tree.

  [ bp: Massage commit message. ]
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/a9351615-7a0d-9d47-af65-d9e2fffe8192@siemens.com

arch/x86/mm/pat/memtype.c

@@ -800,6 +800,7 @@ void memtype_free_io(resource_size_t start, resource_size_t end)
 	memtype_free(start, end);
 }
 
+#ifdef CONFIG_X86_PAT
 int arch_io_reserve_memtype_wc(resource_size_t start, resource_size_t size)
 {
 	enum page_cache_mode type = _PAGE_CACHE_MODE_WC;
@@ -813,6 +814,7 @@ void arch_io_free_memtype_wc(resource_size_t start, resource_size_t size)
 	memtype_free_io(start, start + size);
 }
 EXPORT_SYMBOL(arch_io_free_memtype_wc);
+#endif
 
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 				unsigned long size, pgprot_t vma_prot)