tpm_tis: Introduce intermediate layer for TPM access

This splits tpm_tis in a high-level protocol part and a low-level interface
for the actual TPM communication. The low-level interface can then be
implemented by additional drivers to provide access to TPMs using other
mechanisms, for example native I2C or SPI transfers, while still reusing
the same TIS protocol implementation.

Though the ioread/iowrite calls cannot fail, other implementations of this
interface might want to return error codes if their communication fails.

This follows the usual pattern of negative values representing errors and
zero representing success. Positive values are not used (yet).

Errors are passed back to the caller if possible. If the interface of a
function does not allow that, it tries to do the most sensible thing it
can, but this might also mean ignoring the error in this instance.

This commit is based on the initial work by Peter Huewe.

Signed-off-by: Alexander Steffen <[email protected]>
Signed-off-by: Christophe Ricard <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Tested-by: Jarkko Sakkinen <[email protected]>
Tested-by: Stefan Berger <[email protected]>
Reviewed-by: Stefan Berger <[email protected]>
Signed-off-by: Jarkko Sakkinen <[email protected]>

Author: cricard13