Reverse the meaning of the fit_config_verify() return code

It is more common to have 0 mean OK, and -ve mean error. Change this
function to work the same way to avoid confusion.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/image-fit.c b/common/image-fit.c
index 732505a..40c7e27 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -1534,7 +1534,7 @@
 			images->fit_uname_cfg = fit_uname_config;
 			if (IMAGE_ENABLE_VERIFY && images->verify) {
 				puts("   Verifying Hash Integrity ... ");
-				if (!fit_config_verify(fit, cfg_noffset)) {
+				if (fit_config_verify(fit, cfg_noffset)) {
 					puts("Bad Data Hash\n");
 					bootstage_error(bootstage_id +
 						BOOTSTAGE_SUB_HASH);