anv: Stall before fast-clear operations

anv: Stall before fast-clear operations

During initial CCS bring-up, I discovered that you have to do a full CS
stall prior to doing a CCS resolve as well as afterwards.  It appears
that the same is needed for fast-clears as well.  This fixes rendering
corruptions on The Talos Principle on Sky Lake GT4.  The issue hasn't
been demonstrated on any other hardware however, given that this appears
to be a "too many things in the pipe" problem, having it be easier to
reproduce on a system with more EUs makes sense.  The issues with
resolves is demonstrable on a GT3 or GT2 so this is probably also a
problem on all GTs.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Cc: "13.0 17.0" <mesa-stable@lists.freedesktop.org>