drm/amdgpu: Add bounds checking to ib_{get,set}_value

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: Add bounds checking to ib_{get,set}_value The uvd/vce/vcn code accesses the IB at predefined offsets without checking that the IB is large enough. Check the bounds here. The caller is responsible for making sure it can handle arbitrary return values. Also make the idx a uint32_t to prevent overflows causing the condition to fail.