configs: sandbox: enable mbedtls

Enable mbedtls to have at least one config with
mbedtls enabled.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 718e4a8..1258044 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -352,6 +352,8 @@
 CONFIG_ADDR_MAP=y
 CONFIG_CMD_DHRYSTONE=y
 CONFIG_MBEDTLS_LIB=y
+CONFIG_MBEDTLS_LIB_CRYPTO=y
+CONFIG_HKDF_MBEDTLS=y
 CONFIG_ECDSA=y
 CONFIG_ECDSA_VERIFY=y
 CONFIG_TPM=y