drm: sti: add VTAC drivers

Video Traffic Advance Communication Rx and Tx drivers are designed
for inter-die communication.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/sti/Makefile b/drivers/gpu/drm/sti/Makefile
index 1759c20..1534d4c 100644
--- a/drivers/gpu/drm/sti/Makefile
+++ b/drivers/gpu/drm/sti/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_DRM_STI) = \
-	sti_vtg.o
+	sti_vtg.o \
+	sti_vtac.o
\ No newline at end of file