nvc0: re-validate images after launching a grid on Fermi

Images invalidation is a bit weird on Fermi and there is already a hack
which forces invalidating all images when launching a computer shader
to help in fixing 3D<->CP interaction.

However, we need to re-validate images for compute because
nvc0_compute_invalidate_surfaces() will destroy the previous binding.
This is not really good for performance purposes but this might be
improved later.

This fixes the following piglits:
- spec/arb_compute_shader/execution/basic-uniform-access
- spec/arb_compute_shader/execution/mutiple-texture-reading
- spec/arb_compute_shader/execution/multiple-workgroups
- spec/glsl-4.30/execution/built-in-functions/cs-* (207 tests)

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: "12.0" <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 43d3ecfb33)

src/gallium/drivers/nouveau/nvc0/nvc0_compute.c

@@ -458,4 +458,7 @@ nvc0_launch_grid(struct pipe_context *pipe, const struct pipe_grid_info *info)
 
    /* TODO: Not sure if this is really necessary. */
    nvc0_compute_invalidate_surfaces(nvc0, 5);
+   nouveau_bufctx_reset(nvc0->bufctx_cp, NVC0_BIND_CP_SUF);
+   nvc0->dirty_cp |= NVC0_NEW_CP_SURFACES;
+   nvc0->images_dirty[5] |= nvc0->images_valid[5];
 }