only update tpm if version if not default value

Change-Id: I697de80aa2f0454164cd3651e5a53d06e60a837e

BUG=2782
TEST=boot tested

Review URL: http://codereview.chromium.org/6677067
(cherry picked from commit 55db6a67176a4933427d2ee556180f6e814f60d9)

Review URL: http://codereview.chromium.org/6673067
1 file changed