rockchip: rk3399: add simplest sdram to fix compiling error

This patch is only to make building happy, the real sdram driver
comes later.

BRANCH=none
BUG=none
TEST=emerge-kevin coreboot

Change-Id: I4123c3a6627d7264c615fefbb89e16c4dfb9a423
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 5b992a7895a72c83f57228d3abd1ae37d55e7e7b
Original-Change-Id: Ie340877e828ae760169ccfa9a7099e7472d2fc26
Original-Signed-off-by: Shunqian Zheng <zhengsq@rock-chips.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/338944
Original-Commit-Ready: Vadim Bendebury <vbendeb@chromium.org>
Original-Tested-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://review.coreboot.org/14703
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
3 files changed