tpm: Reduce duplication in a few functions

Update tpm2_clear() and tpm2_pcr_extend() so that the command size
is not repeated twice. Add a small comment to the latter.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
1 file changed