UVD seems OK generally on Tonga (barring apparently being in low power) but not
with GL_NV_vdpau_interop.

Tested with kodi and mpv.

kodi says -

ERROR: VDPAU::COutput error mapping surface
DEBUG: CLinuxRendererGL::GetPlaneTextureSize - invalid size 0x0 - 0

mpv -

[vo/opengl] after rendering: OpenGL error INVALID_OPERATION.

glxinfo shows GL_NV_vdpau_interop present.

mesa is of course agd5f, with some llvm build fixes plus a minor modification I
made to advertise level 52 (as ffmpeg cli at least does check).

I'll attach my diff against agd5f mesa just in case I obviously messed up!