i965: Disable regular fast-clears (CCS_D) on gen9+

This partially reverts commit 3e57e949
which caused a bunch of GPU hangs on several Source titles.  To date, we
have no clue why these hangs are actually happening.  This undoes the
final effect of 3e57e949 and gets us back to not hanging.  Tested
with Team Fortress 2.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102435
Fixes: 3e57e949
Cc: mesa-stable@lists.freedesktop.org
(cherry picked from commit ee57b15e)