drm/radeon: set the full cache bit for fences on r7xx+

Needed to properly flush the read caches for fences.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

diff --cc drivers/gpu/drm/radeon/r600.c
Simple merge

diff --cc drivers/gpu/drm/radeon/r600d.h
Simple merge