Using new usbhost function usb_device_get_string_ucs2() to get USB descriptor strings.

Bug: 70163357
Test: Manual - Connect NuForce (micro) DAC. Examine device name descriptor string.
Note also that it doesn't reboot the device on connection. Verify that audio
plays correctly.

Change-Id: I4b607c51a951cf503fde0b485793dfc9e593f932