drm/amd/display: Bypass gamma set if not standard type

If non-standard gamma type detected set identity matrix flag
so that we can bypass the gamma mode.

Signed-off-by: John Barberiz <jbarberi@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>