examples: Fix memory leaked by device discovery

https://bugs.freedesktop.org/show_bug.cgi?id=105427

examples/img_capture.c

@@ -57,6 +57,7 @@ int main(void)
 
 	ddev = discover_device(discovered_devs);
 	if (!ddev) {
+		fp_dscv_devs_free(discovered_devs);
 		fprintf(stderr, "No devices detected.\n");
 		goto out;
 	}