Fix vboot_reference-firmware linking error

Change-Id: I54052f6d15b9afa52944bf04e09924a3ddb8922e

BUG=none
TEST=emerge-arm-generic vboot_reference-firmware && emerge-arm-generic chromeos-u-boot-next (running)

Review URL: http://codereview.chromium.org/6792031
2 files changed