sandbox: config: Enable FIT signatures with RSA

We want to sign and verify images using sandbox, so enable these options.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/configs/sandbox.h

@@ -43,6 +43,8 @@
 #define CONFIG_OF_LIBFDT
 #define CONFIG_LMB
 #define CONFIG_FIT
+#define CONFIG_FIT_SIGNATURE
+#define CONFIG_RSA
 #define CONFIG_CMD_FDT
 
 #define CONFIG_FS_FAT