drm/sti: remove duplicate object names

When merging 2 drivers common object files were not deduplicated.

Fixes: dcec16ef ("drm/sti: Build monolithic driver")
Cc: stable@kernel.org
Signed-off-by: Rolf Eike Beer <eb@emlix.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/1920148.tdWV9SEqCh@devpool47.emlix.com


Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>