ODROID-C5: board: Add to get correct boot media device

The environment values must be stored in the correct boot media that
is selected by SoC to mitigate storing to a wrong boot media.

Signed-off-by: Dongjin Kim <tobetter@gmail.com>
Change-Id: I4987e65d8c440c545386b3e188c3fc0934f6c470
1 file changed