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: 62e1dcced4b8 ("mm, x86: fix HIGHMEM64 && PARAVIRT build config for native_pud_clear()")
Fixes: 613335b9fc41 ("mm, x86: add support for PUD-sized transparent hugepages")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Thomas Garnier <thgarnie@google.com>
Link: http://lkml.kernel.org/r/20170314121330.182155-1-arnd@arndb.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>