config: exynos: trats2: Enable support for Image.itb at trats2 device

After this change it is possible to boot trats2 device with Image.itb,
which facilitates automated testing, since only one file is necessary.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>