usb: remove device_descriptor buffer, store bytes in UsbDevice.inner instead

examples/stm32f3/src/bin/usb_serial.rs

@@ -54,7 +54,6 @@ async fn main(_spawner: Spawner) {
 
     // Create embassy-usb DeviceBuilder using the driver and config.
     // It needs some buffers for building the descriptors.
-    let mut device_descriptor = [0; 256];
     let mut config_descriptor = [0; 256];
     let mut bos_descriptor = [0; 256];
     let mut control_buf = [0; 7];
@@ -64,7 +63,6 @@ async fn main(_spawner: Spawner) {
     let mut builder = Builder::new(
         driver,
         config,
-        &mut device_descriptor,
         &mut config_descriptor,
         &mut bos_descriptor,
         &mut [], // no msos descriptors