test: compression: add zstd uncompression test

Signed-off-by: Brandon Maier <brandon.maier@collins.com>
diff --git a/configs/sandbox_spl_defconfig b/configs/sandbox_spl_defconfig
index 4d70466..5316e0b 100644
--- a/configs/sandbox_spl_defconfig
+++ b/configs/sandbox_spl_defconfig
@@ -239,6 +239,7 @@
 CONFIG_RSA_VERIFY_WITH_PKEY=y
 CONFIG_TPM=y
 CONFIG_LZ4=y
+CONFIG_ZSTD=y
 CONFIG_ERRNO_STR=y
 CONFIG_SPL_HEXDUMP=y
 CONFIG_UNIT_TEST=y