drm/amd/amdgpu/gfx_v6_0: Supply description for 'gfx_v6_0_ring_test_ib()'s 'timeout' param

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

 drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c:1903: warning: Function parameter or member 'timeout' not described in 'gfx_v6_0_ring_test_ib'
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>

drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c

@@ -1894,6 +1894,7 @@ static void gfx_v6_0_ring_emit_ib(struct amdgpu_ring *ring,
  * gfx_v6_0_ring_test_ib - basic ring IB test
  *
  * @ring: amdgpu_ring structure holding ring information
+ * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
  *
  * Allocate an IB and execute it on the gfx ring (SI).
  * Provides a basic gfx ring test to verify that IBs are working.