rk3288: slowly raise to max cpu voltage to prevent overshoot

slowly raise to max cpu voltage to prevent overshoot,
and in our experience,when cpu run in 1.8GHz,the
vdd_cpu must up to 1.4V

BUG=chrome-os-partner:32716, chrome-os-partner:31896
TEST=Boot on veyron_pinky rev2,check the rk808 buck1 voltage 1400mv
     and measure the overshoot is 1440mv

Change-Id: I759840bd8cf57a5589bf1862d04803f80f804164
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 567f616ff091883ed3275b407859c9399db981b2
Original-Change-Id: I9bb739b49ae4b4f7a60133fa38b0fe51b95c0d78
Original-Signed-off-by: huang lin <hl@rock-chips.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/226753
Original-Reviewed-by: Doug Anderson <dianders@chromium.org>
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/9408
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
2 files changed