odroid-xu3: config: enable DFU/THOR/UMS by add configs and environment

This patch enables all functions required to use DFU/THOR and UMS:
- DWC3: core, gadget, Samsung DWC3 PHY
- USB gadget: endpoint autoconf, downloader, DFU, THOR, UMS

The CONFIG_EXTRA_ENV_SETINGS from exynos5-common.h is redefined
and appended by dfu environment setting and some system settings.

The boot is still using $distro_boot as previous.

Signed-off-by: Inha Song <ideal.song@samsung.com>
Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>