drm/amd/display: Fix SPL related enum definition used in DCN401

Remove a duplicate definition of an SPL related enum transform.h
Since its used in SPL, it has been moved to its own header.

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>