dma-buf: Add selftests for dma-fence

Exercise the dma-fence API exported to drivers.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190819095928.32091-2-chris@chris-wilson.co.uk

drivers/dma-buf/Makefile

@@ -5,5 +5,8 @@ obj-$(CONFIG_SYNC_FILE)		+= sync_file.o
 obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o
 obj-$(CONFIG_UDMABUF)		+= udmabuf.o
 
-dmabuf_selftests-y := selftest.o
+dmabuf_selftests-y := \
+	selftest.o \
+	st-dma-fence.o
+
 obj-$(CONFIG_DMABUF_SELFTESTS)	+= dmabuf_selftests.o

drivers/dma-buf/selftests.h

@@ -10,3 +10,4 @@
  * Tests are executed in order by igt/dmabuf_selftest
  */
 selftest(sanitycheck, __sanitycheck__) /* keep first (igt selfcheck) */
+selftest(dma_fence, dma_fence)