drm/amdgpu: skip the VMID 0 flush for VRAM

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: skip the VMID 0 flush for VRAM Clear-on-release only runs on VRAM, which amdgpu_ttm_map_buffer() reaches via its direct MC address without programming a GART window, yet the wipe still forces a VMID 0 flush. On GFX11 (e.g. Navi33) that spurious SDMA flush can wedge the engine; only flush when a GART window is actually used. v2: Let amdgpu_ttm_map_buffer() return whether the VMID 0 flush is needed, and drive the clear and copy paths from that. (Christian) v3: Make the vm_needs_flush output parameter mandatory instead of allowing NULL. (Christian) (cherry picked from commit a306e406e570b74318ff7d80e5b07b540ca1d3a9)