uboot-imx

Odroid U3: use common code for dram reservation

This commit removes the dram reservation from board file,
because it is done in a common code.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>