i965: Apply post-sync non-zero workaround to homebrew workaround.

i965: Apply post-sync non-zero workaround to homebrew workaround.

In commit 3e5d3626, Eric added a homebrew workaround to fix GPU hangs in
the Mesa "engine" demo and oglc's api-texcoord test.

Unfortunately, his PIPE_CONTROL contains a Depth Stall, which
necessitates the post-sync non-zero workaround,

Fixes GPU hangs in Civilization 4, PlaneShift, and 3DMMES.
Hopefully Heroes of Newerth as well, though I haven't tested that.

NOTE: This is candidate for the 7.11 branch.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=40324
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41096
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-and-tested-by: Eric Anholt <eric@anholt.net>