drm/amdgpu: Fix up kdoc 'ring' parameter in sdma_v6_0_ring_pad_ib

Fix this warning by adding 'ring' arguments to kdoc.

gcc with W=1
drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c:1128: warning: Function parameter or member 'ring' not described in 'sdma_v6_0_ring_pad_ib'

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

drivers/gpu/drm/amd/amdgpu/sdma_v6_0.c

@@ -1121,6 +1121,7 @@ static void sdma_v6_0_vm_set_pte_pde(struct amdgpu_ib *ib,
 /**
  * sdma_v6_0_ring_pad_ib - pad the IB
  * @ib: indirect buffer to fill with padding
+ * @ring: amdgpu ring pointer
  *
  * Pad the IB with NOPs to a boundary multiple of 8.
  */