drm/radeon: fix speaker allocation setup

If the sad_count is 0, set the hw to stereo and change
the error message to a warn.  A lot of monitors don't
set the speaker allocation block.

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

diff --cc drivers/gpu/drm/radeon/dce3_1_afmt.c
Simple merge

diff --cc drivers/gpu/drm/radeon/dce6_afmt.c
Simple merge

diff --cc drivers/gpu/drm/radeon/evergreen_hdmi.c
Simple merge