This commit introduces the emission of a cleaner shader at the end of
the IB submission process. This is achieved by adding a new function
pointer, `emit_cleaner_shader`, to the `amdgpu_ring_funcs` structure. If
the `emit_cleaner_shader` function is set in the ring functions, it is
called during the VM flush process.

The cleaner shader is only emitted if the `enable_cleaner_shader` flag
is set in the `amdgpu_device` structure. This allows the cleaner shader
emission to be controlled on a per-device basis.

By emitting a cleaner shader at the end of the IB submission, we can
ensure that the VM state is properly cleaned up after each submission.

Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Suggested-by: Christian König <christian.koenig@amd.com>