Added documentaion about G2D bindings.

Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

This commit adds a KMS driver for the Tegra20 SoC. This includes basic
support for host1x and the two display controllers found on the Tegra20
SoC. Each display controller can drive a separate RGB/LVDS output.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Mark Zhang <markz@nvidia.com>
Reviewed-by: Mark Zhang <markz@nvidia.com>
Tested-by: Mark Zhang <markz@nvidia.com>
Tested-and-acked-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>