drm/amdgpu/sdma_v4_0: turn off SDMA ring buffer in the s2idle suspend

In the SDMA s0ix save process requires to turn off SDMA ring buffer for
avoiding the SDMA in-flight request, otherwise will suffer from SDMA page
fault which causes by page request from in-flight SDMA ring accessing at
SDMA restore phase.

Link: drm/amd#2248


Cc: stable@vger.kernel.org # 6.0,5.15+
Fixes: f8f4e2a5 ("drm/amdgpu: skipping SDMA hw_init and hw_fini for S0ix.")
Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>