asm-generic: pgalloc.h: use correct #ifdef to enable pud_alloc_one()

The #ifdef statement that guards the generic version of pud_alloc_one() by
mistake used __HAVE_ARCH_PUD_FREE instead of __HAVE_ARCH_PUD_ALLOC_ONE.

Fix it.

Fixes: d9e8b929 ("asm-generic: pgalloc: provide generic pud_alloc_one() and pud_free_one()")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200812191415.GE163101@linux.ibm.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-generic/pgalloc.h

@@ -147,7 +147,7 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
 
 #if CONFIG_PGTABLE_LEVELS > 3
 
-#ifndef __HAVE_ARCH_PUD_FREE
+#ifndef __HAVE_ARCH_PUD_ALLOC_ONE
 /**
  * pud_alloc_one - allocate a page for PUD-level page table
  * @mm: the mm_struct of the current context