tpm driver uses bus=0 as indication of uninitialized tpm device. this change allows 0 as a valid i2c bus number. BUG=None BRANCH=ToT TEST=Built cosmos. Change-Id: Ie8d285abff11643cc3efc0fa30e4afcc3ca1c0d5 Signed-off-by: Patrick Georgi <pgeorgi@chromium.org> Original-Commit-Id: 493077b68cf46b08f0d1ddfe57bf6064d714d537 Original-Change-Id: Iac55e88db4ef757a292270e7201d8fdd37a90b50 Original-Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/226294 Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/9405 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>