anv: add gen9 astc workaround

gen9 does not handle denorms in void extent blocks correctly.  We need
to flush them to zero.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25800>
4 files changed