configs: sandbox: enable padding pss for rsa signature

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 5a744f4..1a76785 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -5,6 +5,7 @@
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
+CONFIG_FIT_ENABLE_RSASSA_PSS_SUPPORT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_BOOTSTAGE=y
 CONFIG_BOOTSTAGE_REPORT=y