drm/amdgpu: enable Vangogh VCN indirect sram mode

commit 9a8cc8ca upstream.

So that uses PSP to initialize HW.

Fixes: 0c2c02b6

 ("drm/amdgpu/vcn: add firmware support for dimgrey_cavefish")
Signed-off-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: James Zhu <James.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>