test: add a test for the new tpm_auto_start() function

A prior patch adds a new API function for TPM2.0, which performs
the full startup sequence of the TPM.  Add a selftest for that.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>