drm/tegra: gem: Flush buffer objects upon allocation

Buffers obtained via shmem may still have associated cachelines. If they
aren't properly flushed they may cause framebuffer corruption if the
cache gets flushed after the application has drawn to it.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc drivers/gpu/drm/tegra/gem.c
Simple merge