Minor refactor on TPM event log blob

Adding a different install_dir than expected by the
recipe is causing build errors. In addition, update the
code organization to match the other blobs for consistency.

Tested: local build succeeded and blobs were installed

Change-Id: Ide93ff52d48a51e54e2ed96b076e73cd18fc3848
Signed-off-by: Ana Mendes <anamendes@google.com>