iris: flush data cache when flushing HDC on GFX < 12
iris: flush data cache when flushing HDC on GFX < 12
This matches what anv driver does.
Fixes: a969ad1d ("iris: Demote DC flush to HDC flush in cache tracker")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6314
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>