Add details about color correction capabilities and explain a bit about
differences between DC hw generations and also how they are mapped
between DRM and DC interface. Two schemas for DCN 2.0 and 3.0 (converted
to svg from the original png) is included to illustrate it. They were
obtained from a discussion[1] in the amd-gfx mailing list.

[1] https://lore.kernel.org/amd-gfx/20220422142811.dm6vtk6v64jcwydk@mail.igalia.com/

v1:
- remove redundant comments (Harry)
- fix typos (Harry)

v2:
- reword introduction of color section
- add co-dev tag for Harry - who provided most of the info
- fix typos (Tales)
- describe missing struct parameters (Tales and Siqueira)
Co-developed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Tales Aparecida <tales.aparecida@gmail.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>