drm/amd/amdgpu/sdma_v6_0: Demote a bunch of half-completed function headers

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

 drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:248: warning: Function parameter or member 'job' not described in 'sdma_v6_0_ring_emit_ib'
 drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:248: warning: Function parameter or member 'flags' not described in 'sdma_v6_0_ring_emit_ib'
 drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:945: warning: Function parameter or member 'timeout' not described in 'sdma_v6_0_ring_test_ib'
 drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:1124: warning: Function parameter or member 'ring' not described in 'sdma_v6_0_ring_pad_ib'
 drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:1175: warning: Function parameter or member 'vmid' not described in 'sdma_v6_0_ring_emit_vm_flush'
 drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:1175: warning: Function parameter or member 'pd_addr' not described in 'sdma_v6_0_ring_emit_vm_flush'

Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>