bl_update: fixed stat() check

src/systemcmds/bl_update/bl_update.c

@@ -74,7 +74,7 @@ bl_update_main(int argc, char *argv[])
 
 	struct stat s;
 
-	if (!stat(argv[1], &s))
+	if (stat(argv[1], &s) != 0)
 		err(1, "stat %s", argv[1]);
 
 	/* sanity-check file size */
@@ -214,4 +214,4 @@ setopt(void)
 
 	errx(1, "option bits setting failed; readback 0x%04x", *optcr);
 
-}
+}