tpm: Enable 'tpmtest' command for Chrome OS boards with TPMs

This command provides a few useful tests so enable it for common boards.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Christophe Ricard<christophe-h.ricard@st.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
diff --git a/configs/snow_defconfig b/configs/snow_defconfig
index 7624ad2..32c7c5d 100644
--- a/configs/snow_defconfig
+++ b/configs/snow_defconfig
@@ -9,6 +9,7 @@
 CONFIG_CMD_PMIC=y
 CONFIG_CMD_REGULATOR=y
 CONFIG_CMD_TPM=y
+CONFIG_CMD_TPM_TEST=y
 CONFIG_SPI_FLASH=y
 CONFIG_CMD_CROS_EC=y
 CONFIG_CROS_EC=y