fixup CI for newly add usb test

refs: #144

Author: wez

xtask/src/lib.rs

@@ -36,6 +36,7 @@ pub static EXAMPLES: &[(&str, &[&str])] = &[
     ("twim-demo", &[]),
     ("twis-demo", &[]),
     ("twis-dma-demo", &[]),
+    ("usb", &[]),
     ("wdt-demo", &[]),
 ];