x86/mm: Remove unused NX related declarations

Since commit 4763ed4 ("x86, mm: Clean up and simplify NX enablement")
these declarations is unused and can be removed.

Signed-off-by: Yue Haibing <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: Yue Haibing

arch/x86/include/asm/pgtable_types.h

@@ -517,8 +517,6 @@ typedef struct page *pgtable_t;
 
 extern pteval_t __supported_pte_mask;
 extern pteval_t __default_kernel_pte_mask;
-extern void set_nx(void);
-extern int nx_enabled;
 
 #define pgprot_writecombine	pgprot_writecombine
 extern pgprot_t pgprot_writecombine(pgprot_t prot);