fit: Remove unused len parameter from fit_get_name()

Remove the unused third parameter (len) from fit_get_name(). All uses of
this function pass NULL for this parameter.

Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>

drivers/fpga/socfpga_arria10.c

@@ -613,7 +613,7 @@ static int first_loading_rbf_to_buffer(struct udevice *dev,
 		images_noffset = fit_conf_get_prop_node_index(buffer_p,
 							     confs_noffset,
 							     FIT_FPGA_PROP, i);
-		uname = fit_get_name(buffer_p, images_noffset, NULL);
+		uname = fit_get_name(buffer_p, images_noffset);
 		if (uname) {
 			debug("FPGA: %s\n", uname);