[PATCH for v4.9 LTS 42/86] drm/amdgpu: check ring being ready before using

From: Ding Pixel [ Upstream commit c5f21c9f878b8dcd54d0b9739c025ca73cb4c091 ] Return success when the ring is properly initialized, otherwise return failure. Tonga SRIOV VF doesn't have UVD and VCE engines, the initialization of these IPs is bypassed. The system crashes if

[PATCH for v4.9 LTS 42/86] drm/amdgpu: check ring being ready before using

From: Ding Pixel [ Upstream commit c5f21c9f878b8dcd54d0b9739c025ca73cb4c091 ] Return success when the ring is properly initialized, otherwise return failure. Tonga SRIOV VF doesn't have UVD and VCE engines, the initialization of these IPs is bypassed. The system crashes if application submit