tegra: fdt: Add LCD definitions for Tegra

Add LCD definitions and also a proposed binding for LCD displays.

The PWM is as per what will likely be committed to linux-next soon.

The displaymode binding comes from a proposal here:

http://lists.freedesktop.org/archives/dri-devel/2012-July/024875.html



The panel binding is new, and fills a need to specify the panel
timings and other tegra-specific information. Should a binding appear
that allows the pwm to handle this automatically, we can revisit
this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>