rk3288: meet the backlight power timing request

backlight timing: LED_VCC->LED_PWM->LED_EN, we modify the
code to meet the timing.

BUG=chrome-os-partner:36201
TEST=Boot from jerry, and scope the backlight timing
BRANCH=None

Change-Id: I6c53a822410ad706383c6d9fa2b5f0437775f710
Signed-off-by: huang lin <hl@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/244639
Reviewed-by: Julius Werner <jwerner@chromium.org>
4 files changed