drm/amdgpu: prevent memory leaks in AMDGPU_CS ioctl

Error out if the AMDGPU_CS ioctl is called with multiple SYNCOBJ_OUT and/or
TIMELINE_SIGNAL chunks, since otherwise the last chunk wins while the
allocated array as well as the reference counts of sync objects are leaked.

Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>