rockchip/rk3399: rockchip: gru/kevin: support sdram 933MHz on kevin

We should be running faster.  Faster = better.

BRANCH=None
BUG=chrome-os-partner:54873
TEST=Boot; stressapptest -M 1028 -s 10000

Change-Id: Iec9343763c1a5a5344959b6e8c4dee8079cf8a20
Signed-off-by: Lin Huang <hl@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/362822
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
4 files changed