clean up arch/x86/mm/pageattr_64.c.

no code changed:

   text    data     bss     dec     hex filename
   1751      16       0    1767     6e7 pageattr_64.o.before
   1751      16       0    1767     6e7 pageattr_64.o.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>