[tpmd] fix compile again

Found while editing the ebuild. Oops!

TEST=build
BUG=chromium-os:32448

Change-Id: Ic02795279eef1204123740fa10e62cd98477c88f
Signed-off-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/33791