Pull x86 fix from Peter Anvin:
 "A single quite small patch that managed to get overlooked earlier, to
  prevent a user space triggerable oops on systems without HPET"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, vdso: Fix an OOPS accessing the HPET mapping w/o an HPET