drm/amdgpu: Add wait IOCTL timeline syncobj support

Add user fence wait IOCTL timeline syncobj support.

v2:(Christian)
  - handle dma_fence_wait() return value.
  - shorten the variable name syncobj_timeline_points a bit.
  - move num_points up to avoid padding issues.

v3:(Christian)
  - Handle timeline drm_syncobj_find_fence() call error
    handling
  - Use dma_fence_unwrap_for_each() in timeline fence as
    there could be more than one fence.

v4:(Christian)
  - Drop the first num_fences since fence is always included in
    the dma_fence_unwrap_for_each() iteration, when fence != f
    then fence is most likely just a container.

v5: Added Alex RB to merge the kernel UAPI changes since he has
    already approved the amdgpu_drm.h changes.

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>