drm/amdgpu: fix another missing fence reference in the CS code

drm/amdgpu: fix another missing fence reference in the CS code

drm_sched_job_add_dependency() consumes the references of the gang
members. Only triggered by mesh shaders.

Signed-off-by: Christian König <christian.koenig@amd.com>
Fixes: 1728baa7e4e6 ("drm/amdgpu: use scheduler dependencies for CS")
Tested-by: Mike Lothian <mike@fireburn.co.uk>
Tested-by: Bert Karwatzki <spasswolf@web.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230105111703.52695-1-christian.koenig@amd.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>