USB: Store device descriptor on enumeration

We now store the device descriptor obtained from the device
during enumeration in the device's object in memory instead
of exposing all of the different members contained within it.

Kernel/Devices/USB/USBDevice.cpp

@@ -94,6 +94,7 @@ KResult Device::enumerate()
     VERIFY(transfer_length > 0);
     m_address = s_next_usb_address++;
 
+    memcpy(&m_device_descriptor, &dev_descriptor, sizeof(USBDeviceDescriptor));
     return KSuccess;
 }