drm/amd/display: Add missing DCE6 SCL_HORZ_FILTER_INIT* SRIs

[ Upstream commit d60f9c45 ]

Without these, it's impossible to program these registers.

Fixes: 102b2f58 ("drm/amd/display: dce_transform: DCE6 Scaling Horizontal Filter Init (v2)")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>