Add another missing header to remove compile time error.
Add another missing header to remove compile time error.

Interestingly, the compile failure is only caused on the buildbot and not my build machine.

Review URL: http://codereview.chromium.org/1239006

acorn-marvell/vboot_reference,geekboxzone/mmallow_external_vboot_reference,marineam/seismograph,coreboot/vboot,marineam/seismograph,ionave/seismograph,marineam/seismograph,geekboxzone/mmallow_external_vboot_reference,acorn-marvell/vboot_reference,coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,geekboxzone/mmallow_external_vboot_reference,coreboot/vboot,acorn-marvell/vboot_reference,ccaapton/vboot_reference,ccaapton/vboot_reference,acorn-marvell/vboot_reference,ionave/seismograph,coreboot/vboot,marineam/seismograph,geekboxzone/mmallow_external_vboot_reference,ccaapton/vboot_reference,ccaapton/vboot_reference,ionave/seismograph,coreboot/vboot