A bit of a hack, but we need to do this until we can do tiled zs in
sysmem (and associated tile/until blits for transfer_map).
Fixes xonotic and glmark2 "refract", when reorder wasn't enabled.
(reorder would paper over the issue by avoiding the extra round-
trip to system memory and back to gmem.
Signed-off-by: Rob Clark <robdclark@gmail.com>