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>
3 files changed