tpm: add Revision ID field in the chip structure

TPM are shipped with a few read-only register from which we can retrieve
for instance:
- vendor ID
- product ID
- revision ID

Product and vendor ID share the same register and are already referenced
in the tpm_chip structure. Add the revision ID entry which is missing.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>