tpm: tpm_tis_i2c: Use a consistent tpm_tis_i2c_ prefix

Use the same prefix on each function for consistency.

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