dm: tpm: Convert the TPM command and library to driver model

Add driver model support to the TPM command and the TPM library. Both
support only a single TPM at present.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Christophe <Ricard&lt;christophe-h.ricard@st.com>
Reviewed-by: Heiko Schocher <hs@denx.de>