Compositor control all the input sub-device (VID, GDP)
and the mixer(s).
It is the main entry point for composition.
Layer interface is used to control the abstracted layers.

Add debug in mixer and GDP.
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: NRob Clark <robdclark@gmail.com>

Generic Display Pipeline are one of the compositor input sub-devices.
GDP are dedicated to graphic input like RGB plans.
GDP is part of Compositor hardware block which will be introduce later.

A sti_layer structure is used to abstract GDP calls from Compositor.
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: NRob Clark <robdclark@gmail.com>