drm/amdgpu: reject oversized IBs with per-ring packet limits

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: reject oversized IBs with per-ring packet limits On GFX rings, amdgpu_cs_p2_ib() passed user-supplied ib_bytes through to ib->length_dw without a limit, while ring_emit_ib() encodes length into packet fields. Oversized values can corrupt adjacent control bits and destabilize command submission. Add a per-ring IB packet size limit helper and reject command submissions exceeding the corresponding dword limit before IB allocation. Use the documented 20-bit limit for GFX/compute/SDMA/VPE, and apply the MM fallback limit for other ring types. (cherry picked from commit 7f48fa2cf62e3fa6c9c3870aa74988f773247e52)

Where it's fixed