drm/amdgpu: fix r initial values

Sriov gets suspend of IP block <dce_virtual> failed as return
value was not initialized.

v2: return 0 directly to align original code semantic before this
was broken out into a separate helper function instead of setting
initial values

Signed-off-by: Victor Zhao <Victor.Zhao@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org