drm/amd/amdgpu: Make afmt_init() cleanup if alloc fails (DCEv11)

Updated DCEv11 afmt_init to cleanup if any kzalloc
fails and then return an error code.  Don't continue initializing
the audio stack in that case.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>