drm/amdgpu: Init MMVM_CONTEXTS_DISABLE in gmc11 golden setting under SRIOV

[Why]
If disable the mmhub vm contexts(set MMVM_CONTEXTS_DISABLE to 0xffff),
driver loading failed on vf due to fence fallback timer expired on all rings.
FLR cannot reset MMVM_CONTEXTS_DISABLE.
So this vf can not be recovered anymore unless trigger a whole gpu reset.

[How]
Under SRIOV, init MMVM_CONTEXTS_DISABLE in gmc11 golden register setting.

Signed-off-by: Yifan Zha <Yifan.Zha@amd.com>
Reviewed-by: Horace Chen <Horace.Chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>