drm/amdgpu: retire support_vmr_ring interface

vmr ring is dedicated for sriov vf (i.e.guest driver
in sriov), which is general communication interface
between driver and psp fw accross all ip version.
it is not correct to make it as ip specific callback.
it is even worse to check specific tOS version per IP
version (like psp_v11/v12).

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>