This patch intend to support save the registers of the DDR controller
and PHY before suspend, and restore them after resume.

Change-Id: Ia10b476c0b837628ac0f365416a7118292753e96
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>