mkimage: Fix missing free() and close() in fit_build()

Make sure that both the error path and normal return free the buffer and
close the file.

Reported-by: Coverity (CID: 138491)
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/tools/fit_image.c b/tools/fit_image.c
index e628212..9d553d1 100644
--- a/tools/fit_image.c
+++ b/tools/fit_image.c
@@ -329,7 +329,7 @@
 	if (ret < 0) {
 		fprintf(stderr, "%s: Failed to build FIT image\n",
 			params->cmdname);
-		goto err;
+		goto err_buf;
 	}
 	size = ret;
 	fd = open(fname, O_RDWR | O_CREAT | O_TRUNC | O_BINARY, 0666);
@@ -346,9 +346,12 @@
 		goto err;
 	}
 	close(fd);
+	free(buf);
 
 	return 0;
 err:
+	close(fd);
+err_buf:
 	free(buf);
 	return -1;
 }