drm/amd: add scheduler fence implementation (v2)

scheduler fence is based on kernel fence framework.

v2: squash in Christian's build fix

Signed-off-by: Chunming Zhou <david1.zhou@amd.com>
Reviewed-by: Christian K?nig <christian.koenig@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile b/drivers/gpu/drm/amd/amdgpu/Makefile
index f1cb7d2..04c2707 100644
--- a/drivers/gpu/drm/amd/amdgpu/Makefile
+++ b/drivers/gpu/drm/amd/amdgpu/Makefile
@@ -86,6 +86,7 @@
 # GPU scheduler
 amdgpu-y += \
 	../scheduler/gpu_scheduler.o \
+	../scheduler/sched_fence.o \
 	amdgpu_sched.o
 
 amdgpu-$(CONFIG_COMPAT) += amdgpu_ioc32.o