usb:dfu:g_dnl: Change number of exported configurations at composite gadget

usb:dfu:g_dnl: Change number of exported configurations at composite gadget

USB composite gadget (g_dnl) supports only one configuration. Due to that
the corresponding field - bConfigurationValue has been changed.

Moreover more descriptive names were chosen for relevant fields.

Windows XP setup:
- Thesyscon USB Descriptor Dumper
- zadig_xp program for WinUSB installation (which is required by dfu-util)
- dfu-util for windows (version 0.6)
- TRATS target connected via USB hub to test Win XP machine.

Tested at: Trats - Exynos4210

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: "Egli, Samuel" <samuel.egli@siemens.com>