FROMLIST: drm/panel: add of display timing support

FROMLIST: drm/panel: add of display timing support

We want add display support on loader, share the same timing
with kernel side, but the timing is hide into kernel code,
can't be share, avoid config twice display timing, add device-tree
display timing support would be good idea.

With this patch, loader and kernel can share same timing from
device node.

Cc: Thierry Reding <thierry.reding@gmail.com>
Change-Id: I6c1ee6ad0194e242035e2f11589d86fdb363b80a
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
(am from https://patchwork.kernel.org/patch/9238727)