mm, x86: fix native_pud_clear build error

mm, x86: fix native_pud_clear build error

We still get a build error in random configurations, after this has been
modified a few times:

  In file included from include/linux/mm.h:68:0,
                   from include/linux/suspend.h:8,
                   from arch/x86/kernel/asm-offsets.c:12:
  arch/x86/include/asm/pgtable.h:66:26: error: redefinition of 'native_pud_clear'
   #define pud_clear(pud)   native_pud_clear(pud)

My interpretation is that the build error comes from a typo in
__PAGETABLE_PUD_FOLDED, so fix that typo now, and remove the incorrect
#ifdef around the native_pud_clear definition.

Fixes: 3e761a42e19c ("mm, x86: fix HIGHMEM64 && PARAVIRT build config for native_pud_clear()")
Fixes: a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages")
Link: http://lkml.kernel.org/r/20170314121330.182155-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Ackedy-by: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>