drm/rockchip/dsi: fix insufficient bandwidth of some panel

drm/rockchip/dsi: fix insufficient bandwidth of some panel

Set the lanes bps to 1 / 0.9 times of pclk, the margin is not enough
for some panel, it will cause the screen display is not normal, so
increases the badnwidth to 1 / 0.8.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1487577744-2855-7-git-send-email-zyw@rock-chips.com