drm/radeon: don't setup audio on asics that don't support it

bug: https://bugzilla.kernel.org/show_bug.cgi?id=97701



Reported-by: Mikael Pettersson <mikpelinux@gmail.com>
Tested-by: Mikael Pettersson <mikpelinux@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org