[MM]: Do not even do the runtime PTRS_PER_{PMD,PUD} checks.

Based upon suggestions from Nick Piggin.
Signed-off-by: David S. Miller <davem@davemloft.net>

mm/memory.c

@@ -2100,7 +2100,6 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
  */
 pud_t fastcall *__pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
 {
-	if (PTRS_PER_PUD > 1) {
 	pud_t *new;
 
 	spin_unlock(&mm->page_table_lock);
@@ -2120,8 +2119,6 @@ pud_t fastcall *__pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long addr
 	pgd_populate(mm, pgd, new);
  out:
 	return pud_offset(pgd, address);
-	}
-	return NULL;
 }
 
 /*
@@ -2135,7 +2132,6 @@ pud_t fastcall *__pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long addr
  */
 pmd_t fastcall *__pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
 {
-	if (PTRS_PER_PMD > 1) {
 	pmd_t *new;
 
 	spin_unlock(&mm->page_table_lock);
@@ -2155,8 +2151,6 @@ pmd_t fastcall *__pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long addr
 	pud_populate(mm, pud, new);
  out:
 	return pmd_offset(pud, address);
-	}
-	return NULL;
 }
 #else
 pmd_t fastcall *__pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)