drm/radeon: fix HDMI quantization_range for pre-DCE5 asics

Support for output_csc is only available on DCE5 and newer so
don't mess with the HDMI quantization_range on pre-DCE5 asics.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=83226

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org