drm/radeon: program DCE2 audio dto just like DCE3

Seems to work like the DCE3 version despite what
the register spec says.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=71975



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