sandbox: tpm: Add TPM emulation

sandbox: tpm: Add TPM emulation

Add a simple TPM emulator for sandbox. It only supports a small subset of
TPM operations. However, these are enough to perform common tasks.

Note this is an initial commit to get this working, but it could use
cleaning up (for example constants instead of open-coded values).

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>