Currently the hikey dsi logic cannot generate accurate byte
clocks values for all pixel clock values. Thus if a mode clock
is selected that cannot match the calculated byte clock, the
device will boot with a blank screen.

This patch uses the new mode_valid callback (many thanks to
Jose Abreu for upstreaming it!) to ensure we don't select
modes we cannot generate.

Also, since the ade crtc code will adjust the mode in mode_set,
this patch also adds a mode_fixup callback which we use to make
sure we are validating the mode clock that will eventually be
used.

Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Xinliang Liu <xinliang.liu@linaro.org>
Cc: Xinliang Liu <z.liuxinliang@hisilicon.com>
Cc: Rongrong Zou <zourongrong@gmail.com>
Cc: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Cc: Chen Feng <puck.chen@hisilicon.com>
Cc: Jose Abreu <Jose.Abreu@synopsys.com>
Cc: Archit Taneja <architt@codeaurora.org>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Xinliang Liu <xinliang.liu@linaro.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>