Odroid-XU3: enable the last dram bank and reserve 22MiB

This commit enables the last DRAM bank and reserves
the last 22 MiB of it, for the secure firmware.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Akshay Saraswat <akshay.s@samsung.com>
Cc: Hyungwon Hwang <human.hwang@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>