common: image_sign_info helper functions in SPL

Do not build image_sign_info helper functions in SPL if not needed.

Fixes: b983cc2da0ba ("lib: rsa: decouple rsa from FIT image verification")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/Kconfig b/Kconfig
index 8bae87e..83b5b05 100644
--- a/Kconfig
+++ b/Kconfig
@@ -447,7 +447,7 @@
 	select SPL_FIT
 	select SPL_RSA
 	select SPL_RSA_VERIFY
-	select IMAGE_SIGN_INFO
+	select SPL_IMAGE_SIGN_INFO
 
 config SPL_LOAD_FIT
 	bool "Enable SPL loading U-Boot as a FIT (basic fitImage features)"