Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/si_dma.c:92: warning: Function parameter or member 'addr' not described in 'si_dma_ring_emit_fence'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:92: warning: Function parameter or member 'seq' not described in 'si_dma_ring_emit_fence'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:92: warning: Function parameter or member 'flags' not described in 'si_dma_ring_emit_fence'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:92: warning: Excess function parameter 'fence' description in 'si_dma_ring_emit_fence'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:252: warning: Function parameter or member 'timeout' not described in 'si_dma_ring_test_ib'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:408: warning: Function parameter or member 'ring' not described in 'si_dma_ring_pad_ib'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:446: warning: Function parameter or member 'vmid' not described in 'si_dma_ring_emit_vm_flush'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:446: warning: Function parameter or member 'pd_addr' not described in 'si_dma_ring_emit_vm_flush'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:446: warning: Excess function parameter 'vm' description in 'si_dma_ring_emit_vm_flush'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:781: warning: Function parameter or member 'ib' not described in 'si_dma_emit_copy_buffer'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:781: warning: Function parameter or member 'tmz' not described in 'si_dma_emit_copy_buffer'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:781: warning: Excess function parameter 'ring' description in 'si_dma_emit_copy_buffer'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:804: warning: Function parameter or member 'ib' not described in 'si_dma_emit_fill_buffer'
 drivers/gpu/drm/amd/amdgpu/si_dma.c:804: warning: Excess function parameter 'ring' description in 'si_dma_emit_fill_buffer'
Acked-by: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>