drm/uapi: Move drm_color_ctm_3x4 out from drm_mode.h

drm/uapi: Move drm_color_ctm_3x4 out from drm_mode.h

drm_color_ctm_3x4 is some undocumented amgdpu private
uapi and thus has no business being in drm_mode.h.
At least move it to some amdgpu specific header, albeit
with the wrong namespace as maybe something somewhere
is using this already?

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Joshua Ashton <joshua@froggi.es>
Cc: Alex Deucher <alexander.deucher@amd.com>
Fixes: 6872a189be50 ("drm/amd/display: Add 3x4 CTM support for plane CTM")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240422085857.17651-1-ville.syrjala@linux.intel.com
Reviewed-by: Harry Wentland <harry.wentland@amd.com>