CVE-2022-49137

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/amdgpu/amdgpu_cs: fix refcount leak of a dma_fence obj

This issue takes place in an error path in
amdgpu_cs_fence_to_handle_ioctl(). When `info->in.what` falls into
default case, the function simply returns -EINVAL, forgetting to
decrement the reference count of a dma_fence obj, which is bumped
earlier by amdgpu_cs_get_fence(). This may result in reference count
leaks.

Fix it by decreasing the refcount of specific object before returning
the error code.