CVE-2026-68250 drm/amdgpu/sdma5.2: replace BUG_ON() with WARN_ON()

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/sdma5.2: replace BUGON with WARNON There's no need to crash the kernel for these cases. cherry picked from commit ae658afc7f47f6147371ec42cc6b1a793dfdb5af...