drm/radeon: fix initial connector audio value

This got lost somewhere along the way.  This fixes
audio not working until set_property was called.

Noticed-by: Hyungwon Hwang <hyungwon.hwang7@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>