Align the behavior of fit_image_verify() called in SPL to the one in full U-Boot. In particular, this function is called when both CONFIG_SPL_LOAD_FIT_FULL and CONFIG_SPL_FIT_SIGNATURE are set (which can happen e.g. in case of secure falcon boot). Reviewed-by: Simon Glass <sjg@chromium.org> Signed-off-by: Francesco Valla <francesco@valla.it>