tpm: Drop two unused options

The address of the I2C TPM is now defined in the device tree so there is no
need for the CONFIG options.

Remove them from the README and board config to avoid confusion.

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