tpm: Remove use of build-time TPM versions

tpm: Remove use of build-time TPM versions

There is only one place in the code which assumes at build-time that we
are using either a v1 or a v2 TPM. Fix this up and add a new function to
return the version of a TPM.

Supported TPM versions (v1 and v2) can be enabled independently and it is
possible to use both versions at once. This is useful for sandbox when
running tests.

Signed-off-by: Simon Glass <sjg@chromium.org>