drm/radeon: use hw generated CTS/N values for audio

commit ee0fec312a1c4e26f255955da942562cd8908a4b upstream.

Use the hw generated values rather than calculating
them in the driver.  There may be some older r6xx
asics where this doesn't work correctly.  This remains
to be seen.

See bug:
https://bugs.freedesktop.org/show_bug.cgi?id=69675



Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>