snow: Enable unit tests

It is useful to have a board with unit tests enabled, to check that this
does not break.

Let's choose snow, since it is not under active development and it is
glorious.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/configs/snow_defconfig b/configs/snow_defconfig
index 6090fea..63a5713 100644
--- a/configs/snow_defconfig
+++ b/configs/snow_defconfig
@@ -92,3 +92,5 @@
 CONFIG_LCD=y
 CONFIG_TPM=y
 CONFIG_ERRNO_STR=y
+CONFIG_UNIT_TEST=y
+# CONFIG_UT_LIB_ASN1 is not set