arm:trats: Enable g_dnl composite USB gadget with embedded DFU function on TRATS

Enable the g_dnl composite USB gadget driver with embedded DFU function on it.
It now uses the composite gadget framework to support download specific
USB functions (like enabled DFU or USB Mass Storage).

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Minkyu Kang <mk7.kang@samsung.com>